©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
Selenocysteylation in Eukaryotes Necessitates the Uniquely Long Aminoacyl Acceptor Stem of Selenocysteine tRNA(*)

(Received for publication, March 27, 1995; and in revised form, May 25, 1995)

Christine Sturchler-Pierrat (1)(§) Nadia Hubert (1) Tsuyoshi Totsuka (2) Takaharu Mizutani (3) Philippe Carbon (1) Alain Krol (1)(¶)

From the  (1)Unit Propre de Recherche 9002 du CNRS ``Structure des Macromolcules Biologiques et Mcanismes de Reconnaissance,'' Institut de Biologie Molculaire et Cellulaire, 15 Rue Ren Descartes, 67084 Strasbourg Cedex, France, the (2)Institute of Developmental Research, Aichi Prefectural Colony for Handicapped, Aichi 480-03, Japan, and the (3)Faculty of Pharmaceutical Sciences, Nagoya City University, Nagoya 467, Japan

ABSTRACT
INTRODUCTION
EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
FOOTNOTES
ACKNOWLEDGEMENTS
REFERENCES

ABSTRACT

Selenocysteine synthesis is achieved on a specific tRNA, tRNA, which is first charged with serine to yield seryl-tRNA. Eukaryotic tRNA exhibits an aminoacyl acceptor stem with a unique length of 9 base pairs. Within this stem, two base pairs, G5a.U67b and U6.U67, drew our attention, whose non-Watson-Crick status is maintained in the course of evolution either through U6.U67 base conservation or base covariation at G5a.U67b. Single or double point mutations were performed, which modified the identity of either or both of the base pairs. Serylation by seryl-tRNA synthetase was unaffected by substitutions at either G5a.U67b or U6.U67. Instead, and quite surprisingly, changing G5a.U67b and U6.U67 to G5a-C67b/U6.G67 or G5a-C67b/C6-G67 gave rise to a tRNA mutant exhibiting a gain of function in serylation. This finding sheds light on the negative influence born by a few base pairs in the acceptor stem of tRNA on its serylation abilities. The tRNA capacities to support selenocysteylation were next examined with regard to a possible role played by the two non-Watson-Crick base pairs and the unique length of the acceptor stem. It first emerges from our study that tRNA transcribed in vitro is able to support selenocysteylation. Second, none of the point mutations engineered at G5a.U67b and/or U6.U67 significantly modified the selenocysteylation level. In contrast, reduction of the acceptor stem length to 8 base pairs led tRNA to lose its ability to efficiently support selenocysteylation. Thus, our study provides strong evidence that the length of the acceptor stem is of prime importance for the serine to selenocysteine conversion step.


INTRODUCTION

Selenocysteine is a cysteine residue in which the thiol group is replaced by the selenol group, SeH. This amino acid has been found in prokaryotic and animal proteins that are generally involved in oxidation-reduction reactions. Selenocysteine is not present in the pool of natural amino acids. Rather, its cotranslational insertion into polypeptide chains responds to a complex biochemical machinery, the mechanism of which has been entirely unraveled in bacteria (see (1) and references therein for review). A specialized selenocysteine, tRNA(^1), is first charged with serine by the conventional seryl-tRNA synthetase. The product seryl-tRNA is subsequently bound by selenocysteine synthase, an enzyme which converts the seryl residue to selenocysteine, using an activated phosphoselenoate compound as the selenium donor. This activated compound is itself the product of the SELD enzyme. Selenocysteine tRNA is then brought to an in frame selenocysteine-specifying UGA codon by SELB, a specific elongation factor different from EF-Tu. Much less is known as to how the eukaryotic machinery fulfills its role. The only identified protein component consists in a fraction containing SELD and selenocysteine synthase-like activities isolated from mouse liver(2) . Eukaryotic selenocysteine tRNAs have been shown for quite some time to recognize the UGA codon and to support serine to selenocysteine conversion(3, 4) . In a previous work(5) , we proposed a secondary and tertiary structure model for vertebrate tRNA. Its secondary structure deviates from that of a classical elongator tRNA by the occurrence, among other structural features, of exceptionally long aminoacyl acceptor and dihydrouracil stems comprising 9 and 6 bp, respectively. On the basis of these unusual characteristics, we asked whether base pairs in, or the unique length of, the acceptor stem, with regard to 7 bp found in the majority of elongator tRNAs, could reflect a function in selenocysteylation. In this work, we first establish that tRNA molecules transcribed in vitro by T7 RNA polymerase can support selenocysteylation in an in vitro assay. Second, we conclude that the length of the acceptor stem constitutes one structural element of tRNA required for the serine to selenocysteine conversion step.


EXPERIMENTAL PROCEDURES

tRNA Constructs

Synthetic bovine wild-type and mutant selenocysteine tRNAs (6) were constructed by hybridizing six couples of 14-24-mer oligodeoxynucleotides containing the desired sequences. The sequences of the oligo couples, which were used to synthesize the wild-type tRNA, are given in Table 1. Mutants were constructed by swapping appropriately one or several couples with oligos containing the substituted sequences. Also included were the promoter of the T7 RNA polymerase immediately 5` to the coding sequence and a BstNI site CCAGG 3` to the coding region to generate the tRNA with a CCA 3`-end after linearization and transcription of the DNA templates. BamHI and EcoRI cloning sites located 5` and 3` to the coding region, respectively, were also incorporated in the oligos. After phosphorylation, the 12 oligos were combined, and the mixture incubated at 90 °C for 10 min and then slowly cooled down to 25 °C. Intermolecular ligation of the oligos and to BamHI/EcoRI-cut pUC119 vector was performed overnight at 16 °C.



In Vitro Transcription by T7 RNA Polymerase

T7 RNA polymerase was prepared from the overexpressing strain Escherichia coli BL21pAR1219 kindly provided by F. William Studier. The purification protocol employed was described in (7) . Conditions for transcription in vitro were as in (5) . The RNA products were purified by gel electrophoresis and electroeluted. When necessary, 10% analytical gels were run and stained with Stains-all for estimation of the ratio of tRNA transcripts carrying an intact CCA end.

Serylation of tRNA

Prior to use, tRNA transcripts were renatured by heating to 65 °C for 3 min and then at 25 °C for 5 min. Aminoacylation occurred in 100 µl of buffer containing 200 mM Tris-HCl, pH 7.4, 20 mM MgCl(2), 20 mM KCl, 10 mM ATP, 40 µM [^3H]serine (29 Ci/mmol). For plateau value determinations, tRNAs were added at a concentration of 3 µM, and the aminoacylation medium was incubated for 5-90 min at 37 °C. Kinetic parameters were determined from three to six independent experiments with tRNA concentrations ranging from 3 to 12 µM. Reactions were started by adding 4 µg of a protein fraction containing partially purified bovine seryl-tRNA synthetase prepared as described in (8) . 20-µl aliquots were transferred onto pieces of Whatman 3 MM paper and submitted to 5% trichloroacetic acid washes. Radioactivity remaining on the filters was measured by scintillation counting.

Selenocysteylation

HSe was prepared enzymatically from radioactive sodium selenite (DuPont NEN) and chromatographically purified according to (2) . In vitro synthesis of [Se]selenocysteyl-tRNA was performed as described in (2) . Briefly, tRNA (25-100 ng) was incubated for 2 h at 30 °C in a 50-µl reaction mixture comprising 200 mM Hepes-NaOH, pH 7.0, 20 mM MgCl(2), 20 mM KCl, 5 mM ATP, 0.4 mM serine, 5 mM 2-mercaptoethanol, 0.7 µM HSe (1-2 µCi), 3 µg of a fraction containing partially purified seryl-tRNA synthetase, and 10 µl of a fraction containing the selenide-activating and selenocysteine synthase activities. After ethanol precipitation, alkaline hydrolysis of the [Se]selenocysteyl-tRNA released [Se]selenocysteine, which was separated by TLC on silicagel G plates in n-butanol:acetic acid:water (4:1:1). Se radioactivity was measured with a Fuji BioImage BAS 2000 analyzer. Cold selenocysteine (a generous gift of Prof. K. Soda, Kyoto University) was cochromatographed as a control and revealed by ninhydrin reaction.


RESULTS

Fig. 1A shows the 9-bp aminoacyl acceptor stem of tRNA and the sequence covariations, which allow its maintenance in the course of evolution(5, 9) . When comparison is restricted to the non-canonical (non-Watson-Crick) base pairs G5a.U67b and U6.U67, one can observe that the latter is strictly conserved in identity. The non-canonical status at position 5a.67b is maintained with, however, a G5a.U67b to A5a.G67b covariation, which was allowed in Drosophila. Conservation of or covariations at non-Watson-Crick base pairs aiming at maintaining a non-canonical status in RNA helices are often indicative of an important structural or functional role played by these particular base pairs(10, 11, 12, 13, 14) . In connection with this and the occurrence of an unusually long acceptor stem, we asked two questions: 1) is there a function devoted to these non-Watson-Crick base pairs and 2) what role can be attributed to the long acceptor stem?


Figure 1: Phylogeny of the acceptor stem in eukaryotic selenocysteine tRNAs and mutant constructs used in this study. A, the vertebrate (Xenopus and mammalian) acceptor stem is shown. Covariations occur in Drosophila at 5-68, 5a.67b, and 5b.67a. A C72 to U72 (in bold) transition is found in Caenorhabditis elegans. The secondary structure is from (5) , and the sequences are from (9) . B, G5a.U67b was replaced by either of the two base pairs mentioned on the left, and U6.U67 was replaced by one of the six base pairs on the right. C, base substitutions at both G5a.U67b and U6.U67, which yielded either G5a-C67b,U6.G67 or G5a-C67b,C6-G67, are indicated. D, identities of the deleted base pairs mentioned in the text, indicated by Delta.



A 2-Base Pair Substitution in the Acceptor Stem Leads to an Improved Serylation Mutant

The first step in the selenocysteine insertion machinery consists in the charging of tRNA with serine. Thus, to determine if the aforementioned non-Watson-Crick base pairs could exert a function, we first wished to know whether altering this base pairing scheme would affect serylation of tRNA. To this end, a series of single or double point mutations was performed, which substituted G5a.U67b and U6.U67 (Fig. 1B). All four possible Watson-Crick pairs and G.U or U.G pairs were engineered by introducing four single and two double point mutations at the U6.U67 base pair. Separately, G5a.U67b was substituted to a Watson-Crick G-C pair and to the non-canonical A.G pair found in Drosophila (Fig. 1B). The tRNA variants carrying these mutations were produced by in vitro transcription with T7 RNA polymerase. The calculated relative V(max)/K values (Table 2) for the mutants compared to wild-type tRNA are in the range of 0.5-3, reflecting an almost negligible effect of the substitutions. We therefore concluded that the replacements made separately at G5a.U67b or U6.U67 did not influence significantly serylation of tRNA. We next produced substitution mutants of both the G5a.U67b and U6.U67 base pairs, giving rise to two different tRNA variants carrying the combined substitutions G5a-C67b/U6.G67 or G5a-C67b/C6-G67 (Fig. 1C). The V(max)/Kratio of G5a-C67b/U6.G67 increased by a factor 6 compared to wild-type tRNA (Table 2). This value results from a decrease in the apparent K (8.5 µM) and an increase in V(max) (475 units). The surprise, however, arose from mutant G5a-C67b/C6-G67, which exhibited a dramatic increase in the V(max)/Kratio, becoming 17.5 times as high as that of wild-type tRNA (Table 2). Both a significant drop in the apparent K value (5 µM) and an increase in the V(max) (875 arbitrary units) contribute to the obtention of this unexpected finding. Thus, point mutations changing G5a.U67b to G5a-C67b or U6.U67 to either U6.G67 or C6-G67 did not provoke significant effects. In marked contrast, the combined substitutions G5a-C67b/U6.G67 and G5a-C67b/C6-G67, and more prominently the latter one generating an almost all G-C pair acceptor stem, endows serylation of these tRNA variants with a higher V(max)/K ratio than the wild type.



Selenocysteylation Is Tolerant to Base Pair Replacements in the Acceptor Stem

Utilization of an in vitro assay for serine to selenocysteine conversion was primarily reported in (2) and is described under ``Experimental Procedures.'' As the assay was originally established for native tRNA purified from bovine liver, a prerequisite was to verify that an in vitro transcribed tRNA (T7tRNA) was also able to support selenocysteylation. Fig. 2A shows this is indeed the case since 25 ng of native tRNA or T7tRNA (lanes1 and 2, respectively) gave rise to [Se]selenocysteine spots of similar intensity. When the number of femtomoles of [Se]selenocysteine produced in the assay by T7tRNA was plotted versus the T7tRNA concentration, the dose-product relationship reached a plateau at 10 nM of tRNA (Fig. 2B). Thus, in further experiments, 25 or 100 ng of T7tRNA, corresponding to approximately 15 and 55 nM in the assay, will be used. All the substitution mutants that changed singly G5a.U67b or U6.U67, or those that substituted both base pairs together (see Fig. 1, B and C), were assayed for their capacities to be selenocysteylated. Table 2reports the percentage of selenocysteylation of the tRNA variants with respect to the in vitro transcribed wild-type tRNA. It ranges from 75% for the U6.U67 to U6.G67 and C6-G67 covariations to 98% for the G5a.U67b to G5a-C67b base replacement. This indicates that values fluctuate moderately and do not deviate significantly from that provided by wild-type tRNA. From these results, we conclude that base replacements or covariations engineered at some targeted base pairs in the amino acceptor arm do not affect selenocysteylation under our conditions.


Figure 2: tRNA transcribed in vitro by T7 RNA polymerase can support efficient selenocysteylation. A, autoradiograph showing selenocysteine produced from tRNA transcribed in vitro (lane1) or native tRNA (lane2). Position of selenocysteine and the origin of the chromatograph are indicated by Sec and O, respectively. B, curve representing the amount of selenocysteine produced versus tRNA concentration under limiting enzyme.



The Length of the Amino Acceptor Arm Is Important for Selenocysteylation

To answer the second question aiming at assigning a specific role to the particularly long acceptor stem, base pair G5a.U67b or U6.U67 was deleted, giving rise to mutant Delta(G5a.U67b) or Delta(U6.U67), represented in Fig. 1D. Aminoacylation kinetics were performed, which indicated that the tRNA deletion mutants possess a slightly better capacity of charging serine than the wild type (Fig. 3). The variability observed in the plateau values is not caused by differences in the tRNA quantities but is rather due to the well known plateau effects, which take into account the spontaneous and enzymatic deacylation of tRNAs(15) . Thus, 100% of charging cannot be attained, and what was observed very likely reflects the effects of the mutations. These deletion mutants were next assayed for their abilities to support serine to selenocysteine conversion. Surprisingly, Table 2shows that both deletions induced a marked down effect on selenocysteine synthesis. However, the intensity of inhibition is not identical in both cases. Delta(U6.U67) still enables the tRNA carrying this deletion to support selenocysteylation to 24% of the wild-type level, while Delta(G5a.U67b) gives rise to only 12% of selenocysteylation, a value that we considered as strongly deleterious. To determine whether this was due to deletion of these particular base pairs or to a more general effect caused by reduction of the stem length to 8 bp, two other deletions, Delta(C3-G70) and Delta(A5b.U67a), were generated, which removed C3-G70 and A5b.U67a, respectively (Fig. 1D). These base pairs are situated at two different locations in the stem. Both deletions conferred mitigating up effects on the serylation capacities of the tRNA variants (Fig. 3). Evaluation of the selenocysteylation abilities of these mutants revealed that both Delta(C3-G70) and Delta(A5b.U67a) achieved a strong repression, leaving 10 and 14% of residual selenocysteylation, respectively (Table 2). Thus, similarly to Delta(G5a.U67b), these deletions led to tRNA variants unable to convert serine to selenocysteine. Incubation of 100 ng, instead of 25 ng, of the four tRNA deletion mutants in the assay did not lead to a proportional increase in selenocysteine synthesis. Indeed, it emerges from Table 2that Delta(C3-G70),Delta(G5a.U67b) and Delta(A5b.U67a), which disabled tRNA when 25 ng were used, marginally improved the selenocysteylation abilities since the deletion mutants allow about 25% of selenocysteine to be made. Likewise, 37% of selenocysteine was obtained with the Delta(U6.U67) mutant under the same conditions. This indicates that the wild-type selenocysteylation abilities abrogated by the base pair deletions could not be significantly restored by augmenting the tRNA amount in the assay, thus corroborating the observations made with 25 ng of tRNA.


Figure 3: Kinetics of serylation of mutant tRNA carrying deletions in the acceptor stem. Plateau values of wild-type and mutant derivatives carrying the base pair deletions are shown in Fig. 1D.



Collectively, our data establish that shortening the tRNA amino acceptor stem to 8 bp is severely detrimental to selenocysteylation in vitro. It appears, however, that removal of U6.U67 leads to a less penalizing effect than deletion of the C3-G70, G5a.U67b, or A5b.U67a base pair.


DISCUSSION

The issues underlying the work presented here originate from inspection of the tRNA secondary structure and sequence comparisons(5, 9) . In the first place, the occurrence of a 9-bp amino acceptor stem, instead of 7 bp in the vast majority of the eukaryotic elongator tRNAs, constituted the central question that guided our investigations. Within this long stem, two non-Watson-Crick base oppositions, G5a.U67b and U6.U67, were shown in our previous work to actually pair in solution(5) . Interestingly, we observed that the non-Watson-Crick (non-canonical) status of base pair U6.U67 is evolutionarily maintained by a strict conservation of both U6 and U67, while the non-canonical status at position 5a.67b subsists during evolution as a result of either sequence conservation or G5a.U67b to A5a.G67b covariation (Fig. 1A). Occurrence of non-Watson-Crick base pairs, their conservation or maintenance by compensatory changes, has been listed in a variety of RNAs such as tRNAs(10, 11) , 5 S RNAs(12) , ribosomal RNAs(13) , and the hammerhead ribozyme(14) , reflecting important structural and/or functional roles.

We elected to disclose the function that could be born by the G5a.U67b and/or U6.U67 base pairs by introducing a series of single or double point mutations at these positions. The first step in selenocysteine synthesis is represented by the charging of tRNA with serine. It was therefore logical to assess beforehand the possible repercussions of the mutations on the serylation of tRNA. None of the single base or base pair replacements carried out separately at G5a.U67b or U6.U67 affected in a significant manner serylation of the tRNA mutants. Much to our surprise, however, the double base pair substitutions G5a-C67b/U6.G67 or G5a-C67b/C6-G67 promoted a strong augmentation of the V(max)/K ratio. This constituted an unpredictable finding from inspection of the tRNA structure. These results underline the notion that tRNA is not optimized for the serylation step. Likewise, it was reported that prokaryotic tRNA is not an excellent substrate for prokaryotic seryl-tRNA synthetase since the K/K value is only 1% that of tRNA(16) .

Two groups of investigators established that the long extra arm and the discriminator base G73 of tRNA function as major identity elements for seryl-tRNA synthetase(17, 18) . Our finding proposes that some base pairs in the acceptor stem can negatively influence serylation of tRNA. In the absence of a structural model describing in detail the interaction between tRNA and seryl-tRNA synthetase, it is perilous to interpret our data. However, it may well be that the seryl-tRNA synthetase establishes base-specific and/or backbone contacts at the acceptor stem of tRNA (serine). These would be disadvantaged by the sequence of some bases in the wild-type tRNA, explaining the revival of activity observed with the two tRNA mutants. This type of contact was reported to contribute, among others, to the interaction between prokaryotic tRNA and seryl-tRNA synthetase(19) .

When it comes to selenocysteylation, the first prominent conclusion of our study resides in the fact that tRNA transcribed in vitro by T7 RNA polymerase can efficiently support selenocysteylation in a similar fashion to native tRNA. This suggests that the structure of the tRNAperse is sufficient to govern recognition by selenocysteine synthase, the lack of modified bases in the tRNA transcript being apparently not redhibitory to selenocysteylation.

Selenocysteylation of the tRNA variants harboring base changes at G5a.U67b and/or U6.U67 revealed that none of the mutants affected the level obtained with the wild-type tRNA transcript. In marked contrast, exploitable information was furnished by reduction to 8 bp of the length of the acceptor stem. All four deletions, Delta(C3-G70), Delta(G5a.U67b), Delta(A5b-U67a), and Delta(U6.U67), impede the selenocysteylation function of the tRNA mutants carrying these deletions. A certain disparity was nevertheless observed in the impediment level since the first three mutants obliterate the activity while Delta(U6.U67) reduces dramatically selenocysteylation but does not abolish it. This was interpreted to mean that the length of the acceptor stem of tRNA plays an important role in the serine to selenocysteine conversion step. Conceivably, the residual level obtained with Delta(U6.U67) could reflect a position-dependent effect of the deletions. One hypothesis would be that selenocysteine synthase not only recognizes the 9-bp acceptor stem but also establishes essential base or backbone-specific contacts with part only of this stem. The U6.U67 deletion would then be less detrimental than others since it is located at the bottom of the stem (Fig. 1A). Alternative possibilities certainly exist, but, as for the serylation mutants, the lack of a model displaying the tRNA-selenocysteine synthase interactions renders highly speculative any structural interpretation. Despite this, it must be stressed that our phenomenological description remains valid and does highlight the prevalent requirement for a 9-bp acceptor stem.

In prokaryotes, the tRNA acceptor stem is 8 bp long(20, 21) , namely 1 base pair longer than canonical tRNAs but 1 base pair shorter than its eukaryotic counterpart. Shortening to 7 bp reduces selenocysteine-synthase activity but does not compromise it, while this shortened stem prevents recognition by SELB, thus enabling EF-Tu to bind tRNA(16) . This finding underscores a notable difference between prokaryotes and eukaryotes for the selenocysteine-synthase recognition elements on tRNA.

The work presented here provides a step toward understanding the mechanisms of eukaryotic serine to selenocysteine conversion. Other issues await answers, for example the purification and cDNA cloning of the eukaryotic SELB counterpart, whose existence was evoked(22, 23, 24) , to decipher the identity of its binding determinants on tRNA. In particular, it might well be that the non-canonical status of base pairs G5a.U67b and U6.U67 is important for recognition of tRNA by the eukaryotic SELB factor.


FOOTNOTES

*
This work was supported by INSERM Grant CRE 920107 and a grant from the Association pour la Recherche contre le Cancer (ARC). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked ``advertisement'' in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

§
Funded by a fellowship from ARC. Present address: Sandoz Pharma Ltd., CH-4002 Basel, Switzerland.

To whom correspondence should be addressed. Tel.: 33-88417050; Fax: 33-88602218; Krol{at}astorg.U-Strasbg.Fr.

^1
The abbreviations used are: tRNA, selenocysteine tRNA; bp, base pair.


ACKNOWLEDGEMENTS

We are grateful to Catherine Florentz and Richard Gieg for helpful discussions. Christine Loegler is thanked for skillful technical assistance and Annie Hoeft for oligonucleotide synthesis.


REFERENCES

  1. Baron, C., and Bck, A. (1995) in tRNA: Structure, Biosynthesis, and Function (Sll, D., and RajBhandary, U. L., eds) pp. 524-544, ASM Press, Washington, D. C.
  2. Mizutani, T., Kurata, H., Yamada, K., and Totsuka, T.(1992)Biochem. J. 284,827-834 [Medline] [Order article via Infotrieve]
  3. Lee, B. J., Worland, P. J., Davis, J. N., Stadtman, T. C., and Hatfield, D. L.(1989) J. Biol. Chem.264,9724-9727 [Abstract/Free Full Text]
  4. Mizutani, T.(1989) FEBS Lett.250,142-146 [CrossRef][Medline] [Order article via Infotrieve]
  5. Sturchler, C. Westhof, E., Carbon, P., and Krol, A.(1993)Nucleic Acids Res. 21,1073-1079 [Abstract]
  6. Amberg, R., Urban, C., Reuner, B., Scharff, P., Pomerantz, S. C., McCloskey, J. A., and Gross, H. J.(1993)Nucleic Acids Res.21,5583-5588 [Abstract]
  7. Zadowski, V., and Gross, H. J.(1991)Nucleic Acids Res.19,1948 [Medline] [Order article via Infotrieve]
  8. Mizutani, T., Narihara, T., and Hashimoto, A.(1984)Eur. J. Biochem.143,9-13 [Abstract]
  9. Lee, B. J., Rajagopalan, M., Kim, Y. S., You, K. H., Jacobson, K. B., and Hatfield, D. L. (1990)Mol. Cell. Biol.10,1940-1949 [Medline] [Order article via Infotrieve]
  10. Quigley, G. J., and Rich, A.(1976)Science194,796-800 [Medline] [Order article via Infotrieve]
  11. Moras, D., Commarmond, M. B., Fischer, J., Weiss, R., Thierry, J. C., Ebel, J. P., and Gieg, R.(1980)Nature 288,669-674 [Medline] [Order article via Infotrieve]
  12. Westhof, E., Romby, P., Romaniuk, P. J., Ebel, J. P., Ehresmann, C., and Ehresmann, B. (1989)J. Mol. Biol.207,417-431 [CrossRef][Medline] [Order article via Infotrieve]
  13. Gautheret, D., Konings, D., and Gutell, R. R.(1994)J. Mol. Biol. 242,1-8 [CrossRef][Medline] [Order article via Infotrieve]
  14. Pley, H. W., Flaherty, K. M., and McKay, D. B.(1994)Nature372,68-74 [CrossRef][Medline] [Order article via Infotrieve]
  15. Dietrich, A., Kern, D., Bonnet, J., and Gieg, R.(1976) Eur. J. Biochem.70,147-158 [Abstract]
  16. Baron, C., and Bck, A.(1991)J. Biol. Chem. 266,20375-20379 [Abstract/Free Full Text]
  17. Wu, X. Q., and Gross, H. J.(1993)Nucleic Acids Res.21,5589-5594 [Abstract]
  18. Ohama, T., Yang, D. C. H., and Hatfield, D. L.(1994)Arch. Biochem. Biophys. 315,293-301 [CrossRef][Medline] [Order article via Infotrieve]
  19. Biou, V., Yaremchuk, A. Tukalo, M., and Cusak, S.(1994)Science 263,1404-1410 [Medline] [Order article via Infotrieve]
  20. Leinfelder, W., Zehelein, E., Mandrand-Berthelot, M. A., and Bck, A.(1988)Nature331,723-725 [CrossRef][Medline] [Order article via Infotrieve]
  21. Baron, C., Westhof, E., Bck, A., and Gieg, R. (1993)J. Mol. Biol.231,274-292 [CrossRef][Medline] [Order article via Infotrieve]
  22. Gelpi, C., Sontheimer, E. J., and Rodriguez-Sanchez, J. L.(1992)Proc. Natl. Acad. Sci. U. S. A.89,9739-9743 [Abstract]
  23. Yamada, K., Mizutani, T., Ejiri, S. I., and Totsuka, T.(1994)FEBS Lett. 347,137-142 [CrossRef][Medline] [Order article via Infotrieve]
  24. Jung, J. E., Karoor, V., Sandbaken, M. G., Lee, B. J., Ohama, T., Gesteland, R. F., Atkins, J. F., Mullenbach, G. T., Hill, K. E., Wahba, A. J., and Hatfield, D. L. (1994)J. Biol. Chem.269,29739-29745 [Abstract/Free Full Text]

©1995 by The American Society for Biochemistry and Molecular Biology, Inc.






This Article
Abstract
Full Text (PDF)
Purchase Article
View Shopping Cart
Alert me when this article is cited
Alert me if a correction is posted
Citation Map
Services
Email this article to a friend
Similar articles in this journal
Similar articles in PubMed
Alert me to new issues of the journal
Download to citation manager
Copyright Permissions
Google Scholar
Articles by Sturchler-Pierrat, C.
Articles by Krol, A.
Articles citing this Article
PubMed
PubMed Citation
Articles by Sturchler-Pierrat, C.
Articles by Krol, A.


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 All ASBMB Journals   Molecular and Cellular Proteomics 
 Journal of Lipid Research   Biochemistry and Molecular Biology Education 
Copyright © 1995 by the American Society for Biochemistry and Molecular Biology.