Department of Virology, Lerner Research Institute, Room # NN-10, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
Correspondence
Amiya Banerjee
banerja{at}ccf.org
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Surprisingly, we found that CypA was not involved in either cellular entry or budding, but rather was required for post-entry primary transcription of VSV-NJ and to a significantly lesser extent, VSV-IND. In addition, both VSV-NJ and VSV-IND virions packaged CypA, although the role of CypA in VSV-NJ infection was more critical compared with its role in VSV-IND infection. These results demonstrate the specific utilization of a host factor by two serologically distinct viruses belonging to the same family, indicating their possible divergence during evolutionary lineages.
![]() |
METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Cyclosporin A and SDZ-211-811 treatment.
To study the effect of cyclosporin A (CsA; Sigma) and SDZ-211-811 (gift from Barbara Willi, Novartis Pharma AG, Basel, Switzerland) treatment on VSV infection, BHK cells were inoculated with either VSV-IND or VSV-NJ (m.o.i.s of 0·1, 1, 2 or 5). Following adsorption for 1 h at 37 °C, the virus-containing medium was removed and fresh medium was added to the washed cells in the presence or absence of CsA (150 µM) or SDZ-211-811 (150 µM). At 6, 12 and 24 h post-infection (p.i.), the medium supernatant from these cells was subjected to plaque assay analysis on L929 cells, as described previously (Zhou et al., 1998). The cell lysates obtained from virus-infected cells (12 h p.i.) were subjected to Western blot analysis with VSV anti-P antibody.
Transfection of mutant CypA cDNA.
Mutant CypA cDNA subcloned into pcDNA (Invitrogen) (a gift from Jim Patrick, Baylor College of Medicine, Houston, Texas, USA) and empty pcDNA vectors were used for the transfection experiment. HeLa cells grown to 7080 % confluency in 24-well plates were transfected with empty vector or mutant CypA cDNA plasmid (700 ng per well) using Lipofectin (Gibco-BRL) as described previously (De et al., 2000). At 36 h post-transfection, the cells were infected with VSV-IND and VSV-NJ (m.o.i. of 0·1). Following adsorption for 1 h at 37 °C, the virus-containing medium was removed and fresh medium was added to the washed cells. At 12 h p.i., cells were lysed and the lysates were subjected to Western blot analysis with VSV anti-P antibody. In addition, the cell lysates obtained from the transfected cells (36 h post-transfection) were subjected to Western blot analysis with anti-CypA antibody to check the overexpression of CypA protein in transfected cells. The medium supernatants from VSV-infected cells (24 h p.i.) were also subjected to plaque assay analysis on L929 cells, as described previously (Zhou et al., 1998
).
Western blot analysis.
At 12 h p.i. (BHK cells) or 36 h post-transfection (HeLa cells), the cells were lysed as described previously (Choudhary et al., 2001). The protein concentration of the cell lysates was determined using a protein assay kit (Bio-Rad), and the cell lysates (10 µg protein) obtained from either BHK or HeLa cells were subjected to 10 % SDS-PAGE followed by Western blotting on to a nitrocellulose membrane. Polyclonal VSV anti-P antibody (Gupta et al., 1998
; Das et al., 1995
) or polyclonal anti-CypA antibody (Saphire et al., 1999
) was used to measure intracellular VSV P protein and CypA, respectively. Protein bands were visualized by staining with horseradish peroxidase-conjugated anti-rabbit antibody (Santa Cruz Biotech) followed by enhanced chemiluminescence according to the manufacturer's protocol (Amersham-Pharmacia Biotech). Similar Western blot analysis with anti-CypA antibody was performed using RNP isolated from purified VSV-IND (6 µg protein), VSV-NJ (6 µg protein) and HPIV-3 (10 µg protein) virions. Western blot analysis with VSV anti-P antibody was also performed using RNP (500 ng protein) isolated from purified VSV-IND and VSV-NJ virions.
In vivo genome transcription of VSV.
To examine the efficiency of VSV genome transcription in vivo in the presence of CsA, BHK cells were infected with VSV-IND or VSV-NJ (m.o.i. of 0·5). Following adsorption for 1 h at 37 °C, fresh medium was added to the washed cells in the presence or absence of CsA (25 µM) and the incubation was continued for an additional 4 h. Actinomycin D (5 µg ml-1; Sigma) was then added to the cells in the presence or absence of CsA and the cells were incubated for an additional 2 h. [3H]Uridine (100 µCi ml-1; Perkin Elmer) was then added to the cellular medium containing actinomycin D in the presence or absence of CsA. After labelling for 4 h at 37 °C, cells were washed and lysed in a lysate buffer containing RNAase inhibitor (Roche). The cell lysates were then subjected to cold 10 % trichloroacetic acid (TCA) precipitation, as described previously (Adam et al., 1986; Manders et al., 1972
). The washed TCA pellet was counted on a gamma counter. The transcription efficiency of VSV genome expressed as percentage transcription, calculated as described in Fig. 4
.
|
Co-immunoprecipitation of VSV N protein with CypA.
For the co-immunoprecipitation analysis, cells were inoculated with VSV-NJ or VSV-IND (m.o.i. of 0·5). Following adsorption for 1 h at 37 °C, fresh medium was added to the washed cells and the incubation was continued for an additional 8 h. Cells were then lysed and the lysates were immunoprecipitated with either a VSV-IND anti-N antibody (which cross-reacts with VSV-NJ N protein; Banerjee et al., 1984; Frazier & Shope, 1979
) or control normal rabbit serum in the presence of washed protein ASepharose beads (Amersham-Pharmacia Biotech). Following incubation for 8 h at 4 °C in a rotor, the beads were washed extensively with PBS and the bound proteins were released from the beads by boiling in the presence of SDS-PAGE sample buffer. The released proteins were subjected to 15 % SDS-PAGE and Western blot analysis with anti-CypA antibody. Similar co-immunoprecipitation analysis was also performed with VSV anti-P and anti-CypA antibodies.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In the absence of a role for CypA in VSV cellular entry, we next investigated whether CypA might have an alternative role in the life-cycle of VSV, such as uncoating, transcription or budding, as observed for HIV-1 (Braaten et al., 1996a, b
; Luban et al., 1993
; Streblow et al., 1998
). For these studies, we infected BHK cells with VSV in the presence of CsA, an immunosuppressant drug that interacts with CypA to alter its conformation and inhibit the prolyl-isomerase activity (Lodish & Kong, 1991
; Steinmann et al., 1991
). A dose response curve with various concentrations of CsA (150 µM) revealed that, at 24 h p.i., VSV-IND replication (m.o.i. of 0·1; Fig. 1
A) was less affected by CsA compared with the significant inhibition of VSV-NJ replication (m.o.i. of 0·1; Fig. 1B
) when CsA was added to the cells following virus adsorption. Since both 25 µM and 50 µM CsA rendered maximal inhibition, we used 25 µM CsA in subsequent studies. To examine the replication capability of VSV following infection in the presence of CsA, a growth kinetics analysis of VSV infectivity (m.o.i. of 0·1) was performed at 6, 12 and 24 h p.i. by plaque assay analysis. As shown in Fig. 1(C, D), C
sA had a significantly reduced effect (inhibition by approximately 1 log) on VSV-IND infection compared with that observed with VSV-NJ (inhibition by 3 logs). Similar results were obtained when cells were infected at higher m.o.i.s of 1, 2 or 5 (data not shown). Western blot analysis (Fig. 1E, F
) of cell lysates obtained at 12 h p.i. from cells infected with VSV in the absence or presence of CsA using VSV anti-P antibody were consistent with the results obtained by plaque assay, i.e. the synthesis of P protein decreased minimally for VSV-IND in the presence of CsA (Fig. 1E
, lanes 3 and 4), whereas the extent of P protein synthesis of VSV-NJ was drastically reduced in the presence of CsA (Fig. 1F
, lanes 3 and 4). Note that there were lower molecular mass bands beneath the VSV P protein in Western blots, which probably represent partially degraded products of the P protein. Western blot analysis of untreated and CsA-treated cell lysates with VSV N protein antibody yielded similar results to those observed with VSV P antibody (data not shown). These data suggested that VSV-NJ, and to a much lesser extent VSV-IND, utilize CypA during infection and that a functional intracellular pool of CypA is required for virus multiplication.
|
|
|
To confirm further the results shown in Fig. 4(A, B) and investigate whether CypA is required during primary transcription of the VSV genome following viral entry, Northern blot analysis was performed with VSV N mRNA. Cells were pretreated with CHX (10 µg ml-1) for 3 h, followed by the addition of VSV in the presence of CHX and in the absence or presence of CsA (25 µM). At 6 h p.i., total RNA was extracted from cells for Northern blot analysis with a VSV N mRNA riboprobe. This method has been utilized previously to monitor intracellular primary transcription of viruses (Choudhary et al., 2001
). As shown in Fig. 4(C)
, the presence of CsA had minimal effect on both steady state VSV-IND mRNA levels (in the absence of CHX) (Fig. 4C
, compare lanes 3 and 6) and primary transcription (in the presence of CHX) (Fig. 4C
, compare lanes 2 and 5) of the VSV-IND genome. Quantification of the VSV-IND N mRNA bands from Fig. 4(C)
revealed less than 15 % inhibition of VSV-IND transcription by CsA (Fig. 4D
). In contrast, both VSV-NJ steady-state mRNA levels (Fig. 4E
, compare lanes 2 and 5) and primary transcription (Fig. 4E
, compare lanes 3 and 6) were drastically inhibited by CsA. Quantification of the VSV-NJ N mRNA bands from Fig. 4(E)
revealed 8590 % inhibition of VSV-NJ transcription by CsA (Fig. 4F
). Similar inhibition in VSV-NJ, but not VSV-IND, RNA synthesis was observed following SDZ-211-88 treatment (data not shown). These results demonstrated that active CypA plays an important role in the primary transcription of VSV genome and that its requirement during this process is selective for VSV-NJ compared with VSV-IND.
CypA interacts with VSV N protein intracellularly and is incorporated into VSV virions
Since viruses are known to incorporate specific host proteins into their virions (Choudhary et al., 2000; Franke et al., 1994
; Gupta et al., 1998
; Thali et al., 1994
), we next examined whether CypA was present in purified VSV virions by subjecting equal amounts (6 µg protein) of RNP purified from VSV-NJ and VSV-IND virions to Western blot analysis with anti-CypA antibody. As shown in Fig. 5
(A), both VSV-IND (lane 3) and VSV-NJ (lane 2) incorporated CypA into its virions, while CypA was not detected in RNP (10 µg protein) isolated from HPIV-3 virions (lane 4). BHK cell lysate was used as the control (lane 1). Similar amounts of VSV-IND and VSV-NJ viral proteins were present in the RNP preparation as deduced by SDS-PAGE and Western blot analysis with VSV anti-P antibody (Fig. 5B, C
). SDS-PAGE analysis of purified RNP (2 µg protein) isolated from VSV-IND (Fig. 5B
, lane 1) and VSV-NJ (Fig. 5B
, lane 2) revealed that equal amounts of N/P proteins were present in both preparations when equal amounts of protein (2 µg protein) were loaded. It is difficult to differentiate between VSV N and P proteins in the gel shown in Fig. 5(B)
, since both N and P proteins of VSV have similar migratory patterns. Nevertheless, Western blot analysis of equal amounts (500 ng protein) of VSV-NJ (Fig. 5C
, lane 1) and VSV-IND (Fig. 5C
, lane 2) RNP preparations with their corresponding anti-P antibody revealed that similar amounts of VSV P were present in both RNP preparations. Moreover, the majority of CypA in purified VSV preparations was bound to viral RNP, since there was no difference in CypA protein levels in purified viruses compared with the RNP isolated from these viruses as deduced by Western blot analysis with anti-CypA antibody (data not shown). Thus, it seems that both VSV serotypes package CypA bound to viral RNP; however, it is preferentially required by the New Jersey serotype for its multiplication.
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
It is important to note that in previous studies with HIV-1 a lower concentration of CsA and SDZ-211-811 (110 µM) was used to inhibit virus replication in immune cells (Braaten & Luban, 2001; Braaten et al., 1996a
, b
) compared with the concentrations used in our studies, where, in BHK cells, maximal inhibition of virus replication occurred in the presence of 25 µM CsA or SDZ-211-811. The requirement for a higher concentration of these drugs to inhibit VSV-NJ replication in non-immune cell culture could be due to the difference in the amount of intracellular CypA present in BHK cells compared with the immune cells (T-lymphocyte Jurkat cells). Moreover, as for BHK cells, 25 µM CsA and SDZ-211-811 was required to inhibit VSV-NJ but not VSV-IND replication efficiently in two additional non-immune cell lines, HeLa (Kopecky et al., 2001
) and A549 (data not shown). Nevertheless, the effects of CsA and SDZ-211-811 on VSV infection were specific, since CsA and SDZ-211-811 at a concentration of 1050 µM failed to inhibit the replication of a related negative-strand RNA virus, HPIV-3, as evaluated by plaque assay (data not shown). CsA is known to inactivate a cytosolic phosphatase, calcineurin, in addition to inhibiting CypA (Alexanian & Bamburg, 1999
). However, the antiviral effect of CsA on VSV-NJ replication was not due to calcineurin inhibition, since neither expression of a calcineurin inhibitor, cain, via adenovirus (Taigen et al., 2000
) nor treatment of cells with a calcineurin inhibitory drug, cypermethrin (Alexanian & Bamburg, 1999
), had any effect on VSV-NJ and VSV-IND replication (data not shown). In addition, the treatment of cells with these drugs (50 µM) was not toxic within the time frame of our experiments (24 h maximum) as deduced by the trypan blue exclusion viability test (data not shown). It is noteworthy that, although in our current studies we used only one subtype of each virus (MuddSummers strain for VSV-IND and Ogden strain for VSV-NJ), it is possible that other subtypes of VSV-IND and/or VSV-NJ may have different requirements for CypA during replication. This line of investigation dealing with subtype-specific requirements for a host protein demands future studies.
CypA belongs to the family of immunophilins and is a peptidyl prolyl-isomerase that acts as a chaperone to maintain proper protein conformation by catalysing the cis-trans isomerization of peptide bonds N-terminal to proline residues (Gothel & Marahiel, 1999; Takahashi et al., 1989
). Several cellular proteins (Steinmann et al., 1991
; Lodish & Kong, 1991
; Schneuwly et al., 1989
; Helekar & Patrick, 1997
) have been shown to be substrates of CypA in vivo. Recently, CypA has also been shown to interact with the HIV-1 capsid and the nucleocapsid domain of HIV-1 Gag polyprotein (Colgan et al., 1996
; Luban et al., 1993
) and is also incorporated into the virions (Franke et al., 1994
; Thali et al., 1994
). However, to date, no definitive stages of the HIV-1 life-cycle that require CypA have been established. Nevertheless, loss of interaction of CypA with HIV-1 Gag results in loss of infection, suggesting an important role for CypA in the HIV-1 life-cycle (Braaten & Luban, 2001
; Saphire et al., 1999
). CypA binds to the capsid protein of HIV-1 to provide functional conformation required for HIV-1 infection (Agresta & Carter, 1997
; Dietrich et al., 2001
; Streblow et al., 1998
) following proline isomerization. Our current studies have demonstrated that functional CypA is also required for VSV infection and that in infected cells CypA binds to the N protein, which encapsidates the viral genome, similar to the CypA-binding capsid protein of HIV-1 (Agresta & Carter, 1997
). Based on these similarities, one may speculate that CypA binds to the VSV N protein to isomerize the proline residues required for proper functional folding of the N protein.
One intriguing observation of the current investigation is the striking difference in requirement for CypA by VSV-NJ compared with VSV-IND. Functional CypA is definitely required for VSV-NJ infection and primary transcription, whereas the CypA requirement for VSV-IND is minimal compared with VSV-NJ, although both viruses incorporate CypA into their virions. It is interesting to note that a similar correlation exists between the HIV-1 isolates in relation to their requirement for CypA for infection. For example, HIV-2 and SIV, which belong to the same family of viruses as HIV-1, do not require CypA for infection (Braaten et al., 1996b). In addition, among the HIV-1 subtypes, group main (M) HIV-1, but not group outlier (O) HIV-1, requires CypA, although isolates of group O HIV-1 incorporate CypA into their virions (Braaten et al., 1996b
). Most interestingly, the replication of a primary wild-type isolate of HIV-1-Eli was found to be more sensitive to the presence of intracellular CypA compared with the laboratory strain HIV-1-NL4-3, although both isolates interacted with CypA (Braaten & Luban, 2001
). Based on our findings that VSV-NJ (the prevailing virulent VSV strain in the wild; Rodriguez & Nichol, 1999
) critically requires functional CypA for replication, in contrast to VSV-IND (a less virulent and less prevailing VSV serotype in the wild; Rodriguez & Nichol, 1999
), it is tempting to speculate that the two viruses have evolved from an ancestral VSV that was initially dependent on CypA for replication. During evolutionary divergence from the ancestral lineages, VSV-IND may have adapted to reduce its dependency on CypA, possibly as a result of evolutionary pressure. Indeed, phylogenetic analysis of these two serotypes of VSV has revealed that VSV-NJ has diverged less from the VSV ancestor than VSV-IND (Bilsel & Nichol, 1990
). It is thus possible that, due to this adaptation, VSV-IND utilizes host chaperones other than CypA, including heat-shock proteins (HSPs) and other immunophilins.
Our results suggest that the requirement for CypA in VSV infection could be at the level of primary transcription. It is plausible that by virtue of CypA's interaction with VSV N protein the nucleocapsids are folded into a transcriptionally competent conformation. Such stringent structural requirements (a helical extended structure) of the VSV N protein for transcription have been previously demonstrated (De et al., 1982; Heggeness et al., 1980
). Thus, the interaction of N with CypA could result in the formation of the correct structure required for optimal transcription efficiency of the VSV-NJ genome. This scenario could be similar to the interaction of CypA with the Gag protein of HIV-1. The binding of CypA to the HIV-1 capsid (which, like the N protein, encapsidates the HIV-1 genome RNA) protein oligomers led to the formation of an elongated compact structure, the functional conformation required for efficient HIV-1 infection (Agresta & Carter, 1997
; Braaten et al., 1996a
; Streblow et al., 1998
).
Finally, the role of chaperones in the transcription of the virus genome has been documented for several viruses. For example, binding of the chaperonin complex HSP 90, 70 and p23 to the N protein of hepatitis B virus (Hu et al., 1997, 2002
) results in the optimal conformation of N required for efficient reverse transcription and RNP formation. It is interesting to note that earlier studies have reported cyclophilins functioning as a cellular chaperonin complex along with HSPs (Jakob & Buchner, 1994
; Sanchez & Ning, 1996
; Uittenbogaard et al., 1998
). For example, the HSP and cyclophilin complex have been shown to be involved in correct folding of steroid receptors (Jakob & Buchner, 1994
; Sanchez & Ning, 1996
). Whether CypA along with HSP or other chaperonin protein(s) forms a complex to facilitate VSV genome transcription remains to be elucidated. Coupled with the fact that HIV-1 packages CypA (Franke et al., 1994
; Thali et al., 1994
) and HSP 70 (Gurer et al., 2002
), earlier studies have demonstrated that VSV-NJ also incorporates HSP 70 into its virions (Sagara & Kawai, 1992
) and that the N protein of VSV interacts with HSP in infected cells (Garry et al., 1983
). Thus, these observations, together with our current studies of CypA, ascertain the importance of cellular chaperones in VSV infection. Our current study has thus highlighted the essential role of the chaperone protein CypA, a member of the cellular protein-folding machinery in VSV transcription and infection. Since VSV-NJ is the highly virulent strain of VSV known to cause disease and high mortality among economically important livestock, the requirement for CypA for its replication could serve as a potential target for antiviral agents.
![]() |
ACKNOWLEDGEMENTS |
---|
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Agresta, B. E. & Carter, C. (1997). Cyclophilin a induced alterations of human immunodeficiency virus type 1 CA protein in vitro. J Virol 71, 69216927.[Abstract]
Alexanian, A. R. & Bamburg, J. R. (1999). Neuronal survival activity of s100 is enhanced by calcineurin inhibitors and requires activation of NF-
B. FASEB J 13, 16111620.
Banerjee, A. K. (1987). Transcription and replication of rhabdoviruses. Microbiol Rev 51, 6687.[Medline]
Banerjee, A. K., Rhodes, D. P. & Gill, D. S. (1984). Complete nucleotide sequence of the mRNA coding for the N protein of vesicular stomatitis virus (New Jersey serotype). Virology 137, 432438.[Medline]
Barik, S. & Banerjee, A. K. (1992). Phosphorylation by cellular casein kinase II is essential for transcriptional activity of vesicular stomatitis virus phosphoprotein P. Proc Natl Acad Sci U S A 89, 65706574.[Abstract]
Billich, A., Hammerschmid, F., Peichl, P., Wenger, R., Zenke, G., Quesniaux, V. & Rosenwirth, B. (1995). Mode of action of SDZ NIM 811, a nonimmunosuppressive cyclosporin A analog with activity against human immunodeficiency virus (HIV) type 1: interference with HIV proteincyclophilin A interactions. J Virol 69, 24512461.[Abstract]
Bilsel, P. A. & Nichol, S. T. (1990). Polymerase errors accumulating during natural evolution of the glycoprotein gene of vesicular stomatitis virus Indiana serotype isolates. J Virol 64, 48734883.[Medline]
Bose, S. & Banerjee, A. K. (2002). Role of heparan sulfate in human parainfluenza virus type 3 infection. Virology 298, 7383.[CrossRef][Medline]
Bose, S., Malur, A. & Banerjee, A. K. (2001). Polarity of human parainfluenza virus type 3 infection in polarized human lung epithelial A549 cells: role of microfilament and microtubule. J Virol 75, 19841989.
Braaten, D. & Luban, J. (2001). Cyclophilin A regulates HIV-1 infectivity, as demonstrated by gene targeting in human T cells. EMBO J 20, 13001309.
Braaten, D., Franke, E. K. & Luban, J. (1996a). Cyclophilin is required for an early step in the life cycle of human immunodeficiency virus type 1 before the initiation of reverse transcription. J Virol 70, 35513560.[Abstract]
Braaten, D., Franke, E. K. & Luban, J. (1996b). Cyclophilin A is required for the replication of group M human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus SIVCPZGAB but not group O HIV-1 or other primate immunodeficiency viruses. J Virol 70, 42204227.[Abstract]
Chong, D. D. & Rose, J. K. (1993). Membrane association of functional vesicular stomatitis virus matrix protein in vivo. J Virol 67, 407414.[Abstract]
Choudhary, S., De, B. P. & Banerjee, A. K. (2000). Specific phosphorylated forms of glyceraldehyde 3-phosphate dehydrogenase associate with human parainfluenza virus type 3 and inhibit viral transcription in vitro. J Virol 74, 36343641.
Choudhary, S., Gao, J., Leaman, D. W. & De, B. P. (2001). Interferon action against human parainfluenza virus type 3: involvement of a novel antiviral pathway in the inhibition of transcription. J Virol 75, 48234831.
Colgan, J., Yuan, H. H., Franke, E. K. & Luban, J. (1996). Binding of the human immunodeficiency virus type 1 gag polyprotein to cyclophilin A is mediated by the central region of capsid and requires gag dimerization. J Virol 70, 42994310.[Abstract]
Das, T., Gupta, A. K., Sims, P. W., Gelfand, C. A., Jentoft, J. E. & Banerjee, A. K. (1995). Role of cellular casein kinase II in the function of the phosphoprotein (P) subunit of RNA polymerase of vesicular stomatitis virus. J Biol Chem 270, 2410024107.
Das, T., Mathur, M., Gupta, A. K., Janssen, G. M. & Banerjee, A. K. (1998). RNA polymerase of vesicular stomatitis virus specifically associates with translational elongation factor-1 for its activity. Proc Natl Acad Sci U S A 95, 14491454.
De, B. P., Thornton, G. B., Luk, D. & Banerjee, A. K. (1982). Purified matrix protein of vesicular stomatitis virus blocks viral transcription in vitro. Proc Natl Acad Sci U S A 79, 71377141.[Abstract]
De, B. P., Lesoon, A. & Banerjee, A. K. (1991). Human parainfluenza virus type 3 transcription in vitro: role of cellular actin in mRNA synthesis. J Virol 65, 32683275.[Medline]
De, B. P., Hoffman, M. A., Choudhary, S., Huntley, C. C. & Banerjee, A. K. (2000). Role of NH2 and COOH terminal domains of the P protein of human parainfluenza virus type 3 in transcription and replication. J Virol 74, 58865895.
Dietrich, L., Ehrlich, L. S., LaGrassa, T. J., Ebbets-Reed, D. & Carter, C. (2001). Structural consequences of cyclophilin A binding on maturational refolding in human immunodeficiency virus type 1 capsid protein. J Virol 75, 47214733.
Dorfman, T. & Gottlinger, H. G. (1996). Capsid p2 domain confers sensitivity to the cyclophilin binding drug SDZ NIM 811. J Virol 70, 57515757.[Abstract]
Franke, E. K., Yuan, H. E. & Luban, J. (1994). Specific incorporation of cyclophilin A into HIV-1 virions. Nature 372, 359362.[CrossRef][Medline]
Frazier, C. L. & Shope, R. E. (1979). In Rhabdoviruses, vol. 1, pp. 4363. Edited by D. H. L. Bishop. Boca Raton: CRC Press.
Garry, R. F., Ulug, E. T. & Bose, H. R. (1983). Induction of stress proteins in Sindbis virus and vesicular stomatitis virus infected cells. Virology 129, 319332.[Medline]
Gothel, S. F. & Marahiel, M. A. (1999). Peptidyl-prolyl cis-trans isomerases, a superfamily of ubiquitous folding catalysts. Cell Mol Life Sci 55, 423436.[CrossRef][Medline]
Gupta, A. K. & Banerjee, A. K. (1997). Expression and purification of NP complex from Escherichia coli: role in genome RNA transcription and replication in vitro. J Virol 71, 42644271.[Abstract]
Gupta, A. K., Drazba, J. A. & Banerjee, A. K. (1998). Specific interaction of heterogenous nuclear ribonucleoprotein particle U with the leader RNA sequence of vesicular stomatitis virus. J Virol 72, 85328540.
Gurer, C., Cimarelli, A. & Luban, J. (2002). Specific incorporation of heat shock protein 70 family members into primate lentiviral virions. J Virol 76, 46664670.
Hanson, R. P. (1952). The natural history of vesicular stomatitis virus. Bacteriol Rev 15, 179204.
Harty, R. N., Paragas, J., Sudol, M. & Palese, P. (1999). A proline-rich motif within the matrix protein of vesicular stomatitis virus and rabies virus interacts with WW domains of cellular proteins: implications for viral budding. J Virol 73, 29212929.
Harty, R. N., Brown, M. E., McGettigan, J. P., Wang, G., Jayakar, H. R., Huibregtse, J. M., Whitt, M. A. & Schnell, M. J. (2001). Rhabdoviruses and the cellular ubiquitinproteasome system: a budding interaction. J Virol 75, 1062310629.
Heggeness, M. H., Scheid, A. & Choppin, P. W. (1980). Conformation of the helical nucleocapsids of paramyxoviruses and vesicular stomatitis virus: reversible coiling and uncoiling induced by changes in salt concentration. Proc Natl Acad Sci U S A 77, 26312635.[Abstract]
Helekar, S. A. & Patrick, J. (1997). Peptidyl-prolyl cis-trans isomerase activity of cyclophilin A in functional homo-oligomeric receptor expression. Proc Natl Acad Sci U S A 94, 54325437.
Hu, J., Toft, D. & Seeger, C. (1997). Hepadnavirus assembly and reverse transcription require a multi-component chaperone complex which is incorporated into nucleocapsids. EMBO J 16, 5968.
Hu, J., Toft, D., Anselmo, D. & Wang, X. (2002). In vitro reconstitution of functional hepadnavirus reverse transcriptase with cellular chaperone proteins. J Virol 76, 269279.
Jakob, U. & Buchner, J. (1994). Assisting spontaneity: the role of Hsp 90 and small Hsps as molecular chaperones. Trends Biochem Sci 19, 205211.[CrossRef][Medline]
Kopecky, S. A., Willingham, M. C. & Lyles, D. S. (2001). Matrix protein and another viral component contribute to induction of apoptosis in cells infected with vesicular stomatitis virus. J Virol 75, 1216912181.
Lodish, H. F. & Kong, N. (1991). Cyclosporin A inhibits an initial step in folding of transferrin within the endoplasmic reticulum. J Biol Chem 266, 1483514838.
Luban, J., Bossolt, K. L., Franke, E. K., Kalpana, G. V. & Goff, S. P. (1993). Human immunodeficiency virus type 1 gag protein binds to cyclophilins A and B. Cell 73, 10671078.[Medline]
Lyles, D. S., McKensie, M. & Parce, J. W. (1992). Subunit interactions of vesicular stomatitis virus envelope glycoprotein stabilized by binding to viral matrix protein. J Virol 66, 349358.[Abstract]
Manders, E. K., Tilles, J. H. & Huang, A. S. (1972). Interferon mediated inhibition of virion directed transcription. Virology 49, 573581.[Medline]
Moyer, S. A., Baker, S. C. & Lessard, J. L. (1986). Tubulin: a factor necessary for the synthesis of both Sendai virus and vesicular stomatitis virus RNAs. Proc Natl Acad Sci U S A 83, 54055409.[Abstract]
Nauwynck, H. J., Duan, X., Favoreel, H. W., VanOostveldt, P. & Pensaert, M. B. (1999). Entry of porcine reproductive and respiratory syndrome virus into porcine alveolar macrophages via receptor mediated endocytosis. J Gen Virol 80, 297305.[Abstract]
Ono, K., Dubois-Dalcq, M. E., Schubert, M. & Lazzarini, R. A. (1987). A mutated membrane protein of vesicular stomatitis virus has an abnormal distribution within the infected cell and causes defective budding. J Virol 61, 13321341.[Medline]
Peluso, R. W. & Moyer, S. A. (1983). Initiation and replication of vesicular stomatitis virus genome RNA in a cell free system. Proc Natl Acad Sci U S A 80, 31983202.[Abstract]
Rodriguez, L. L. & Nichol, S. T. (1999). Vesicular stomatitis viruses. In Encyclopedia of Virology, vol. 5, 2nd edn, pp. 19101919. Edited by A. Granoff & R. G. Webster. San Diego: Academic Press.
Rose, J. K. & Whitt, M. A. (2001). Rhabdoviridae: the viruses and their replication. In Fields Virology, 4th edn, pp. 12211244. Edited by D. M. Knipe & P. M. Howley. Philadelphia: Lippincott Williams & Wilkins.
Sagara, J. & Kawai, A. (1992). Identification of heat shock protein 70 in the rabies virion. Virology 190, 845848.[Medline]
Sanchez, E. R. & Ning, Y. M. (1996). Immunophilins, heat shock proteins, and glucocorticoid receptor actions in vivo. Methods 9, 188200.[CrossRef][Medline]
Saphire, A. C. S., Bobardt, M. D. & Gallay, P. A. (1999). Host cyclophilin A mediates HIV-1 attachment to target cells via heparans. EMBO J 18, 67716785.
Schneuwly, S., Shortridge, R. D., Larrivee, D. C., Ono, T., Ozaki, M. & Pak, W. L. (1989). Drosophilia ninaA gene encodes an eye specific cyclophilin. Proc Natl Acad Sci U S A 86, 53905394.[Abstract]
Steinmann, B., Bruckner, P. & Superti-Furga, A. (1991). Cyclosporin A slows collagen triple helix formation in vivo: indirect evidence for a physiologic role of peptidyl-prolyl cis-trans isomerase. J Biol Chem 266, 12991303.
Streblow, D. N., Kitabwalla, M., Malkovsky, M. & Pauza, C. D. (1998). Cyclophilin A modulates processing of human immunodeficiency virus type 1 p55 gag: mechanism for antiviral effects of cyclosporin A. Virology 245, 197202.[CrossRef][Medline]
Taigen, T., DeWindt, L. J., Lim, H. W. & Molkentin, J. D. (2000). Targeted inhibition of calcineurin prevents agonist induced cardiomyocyte hypertrophy. Proc Natl Acad Sci U S A 97, 11961201.
Takahashi, N., Hayano, T. & Suzuki, M. (1989). Peptidyl-prolyl cis-trans isomerase is the cyclosporin A binding protein cyclophilin. Nature 337, 473475.[CrossRef][Medline]
Thali, M., Bukovsky, A., Kondo, E., Rosenwirth, B., Walsh, C. T., Sodroski, J. & Gottlinger, H. G. (1994). Functional association of cyclophilin A with HIV-1 virions. Nature 372, 363365.[CrossRef][Medline]
Uittenbogaard, A., Ying, Y. & Smart, E. J. (1998). Characterization of a cytosolic heat shock protein caveolin chaperone complex. Involvement in cholesterol trafficking. J Biol Chem 273, 65256532.
Zhou, A., Paranjape, M. J. M., Hassel, B. A., Nie, H., Shah, S., Galinski, B. & Silverman, R. H. (1998). Impact of Rnase L overexpression on viral and cellular growth and death. J Interferon Cytokine Res 18, 953961.[Medline]
Zydowsky, L. D., Etzkorn, F. A., Chang, H. Y., Ferguson, S. B., Stolz, L. A., Ho, S. I. & Walsh, C. T. (1992). Active site mutants of human cyclophilin A separate peptidyl-prolyl isomerase activity from cyclosporin A binding and calcineurin inhibition. Protein Sci 1, 10921099.
Received 25 December 2002;
accepted 24 February 2003.