1 MPI for Molecular Genetics, Ihnestr. 73, 14195 Berlin, Germany
2 LISM, CNRS, 31 chemin Joseph Aiguier, 13402 Marseille, Cedex 20, France
Authors for correspondence (e-mail: laroche{at}ibsm.cnrs-mrs.fr; scherth{at}web.de)
Accepted 3 August 2005
![]() |
Summary |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: Set1, C1b5, Meiosis, Centromere, Telomere, Bouquet
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Fluorescent in situ hybridization (FISH) studies with pan-centromeric and pan-telomeric DNA probes, as well as live cell observations in the yeast Saccharomyces cerevisiae, have shown that induction of the meiotic cycle leads to a dramatic reorganization of nuclear architecture, which resembles the chromosome dynamics observed in meiosis of higher eukaryotes (reviewed by Loidl, 1990; Zickler and Kleckner, 1998
; Scherthan, 2001
). In mitotic yeast nuclei, all centromeres are clustered near the spindle pole body (SPB), a topology which is only reduced when cells are kept stationary for an extended period (Jin et al., 1998
). Soon after induction of meiosis, centromeres lose their intimate association with the SPB and become dispersed throughout the nucleus (Hayashi et al., 1998
; Jin et al., 1998
). By contrast, telomeres, which are grouped into several perinuclear clusters in vegetatively growing cells (Gotta et al., 1996
), disperse over the nuclear periphery and transiently congregate in the vicinity of the SPB to form the so-called bouquet at the leptotene/zygotene transition (Trelles-Sticken et al., 1999
). After the bouquet stage, telomeres again become redistributed randomly over the nuclear periphery during pachytene. Formation of the bouquet depends on the presence of the meiosis-specific telomere protein Ndj1/Tam1 (Chua and Roeder, 1997
; Conrad et al., 1997
; Trelles-Sticken et al., 2000
) and actin polymerization (Trelles-Sticken et al., 2005
). It has been proposed that formation of the bouquet catalyzes the meiotic homologue pairing process (Loidl, 1990
), an idea supported by cytological (Trelles-Sticken et al., 2000
) and genetic (Goldman and Lichten, 2000
; Rockmill and Roeder, 1998
) evidence and clearly demonstrated in the asynaptic meiosis of Schizosaccharomyces pombe (Niwa et al., 2000
).
Various analyses have shown an intimate relationship between premeiotic S phase and the initiation of recombination (Borde et al., 2000). In this respect, the absence of the B-type cyclins Clb5 and Clb6, which are required for premeiotic S phase, leads to a defect in double-strand break (DSB) induction, recombination and synaptonemal complex (SC) formation (Smith et al., 2001
; Stuart and Wittenberg, 1998
). These results suggest that the meiosis-specific chromatin configuration established during premeiotic S phase might be a precondition for later chromosomal interactions.
Set1 belongs to an eight-protein complex responsible for the specific methylation of lysine 4 of histone H3 (Miller et al., 2001; Nagy et al., 2002
; Roguev et al., 2001
). The Set1-mediated H3 lysine 4 methylation has been linked to transcriptional elongation (Krogan et al., 2003
; Ng et al., 2003
). Inactivation of SET1 affects telomere structure and DNA repair activities in mitotic yeast cells (Corda et al., 1999
; Nislow et al., 1997
; Santos-Rosa et al., 2004
; Schramke et al., 2001
) as well as sporulation of diploid cells (Nislow et al., 1997
). The defect in meiotic progression combines with a delay of premeiotic S phase onset, a severe impairment of DSB formation and a limited induction of middle meiotic genes (Sollier et al., 2004
).
To investigate the relationships that exists between replication and chromosomal movements during the meiotic prophase, we followed nuclear dynamics and premeiotic S phase in wild-type SK1 cells as well as in different mutants in which premeiotic replication is delayed, namely clb5, ime2
and set1
.
![]() |
Materials and Methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Cell culture and preparation
For nuclear preparation, cultures were grown in presporulation medium to a density of 2x107 cells/ml and then transferred to sporulation medium (2% potassium acetate) at a density of 4x107 cells/ml (Roth and Halvorson, 1969). Aliquots from the cultures were obtained during time course experiments at 0 minutes as well as 60, 120, 210, 270, 330 and 420 minutes after transfer to sporulation medium. For clb5
, clb5
set1
and set1
mec1-1, additional aliquots were taken at 480 minutes. Aliquots were immediately transferred to tubes on ice containing 1/10 volume of acid-free 37% formaldehyde (Merck). After 30 minutes, cells were removed from the fixative, washed with 1x SSC and spheroplasted with Zymolyase 100T (100 µg/ml; Seikagaku, Tokyo, Japan) in 0.8 M sorbitol, 2% potassium acetate, 10 mM dithiothreitol. Spheroplasting was terminated by adding 10 volumes of ice-cold 1 M sorbitol. Meiotic spreads were obtained and subjected to FISH as described previously (Trelles-Sticken et al., 2000
).
FACS analysis
Meiotic cells were fixed in 70% ethanol. After rehydration in PBS, the samples were incubated for at least 2 hours with RNase A (1 mg/ml) at 37°C. Cells were resuspended in 50 µg/ml propidium iodide in PBS for at least 15 minutes at room temperature. After a wash in PBS, cells were resuspended in 5 µg/ml propidium iodide, sonicated briefly to remove cell clumps if required, and the DNA content was determined by FACS with a Becton Dickinson FASCalibur (BD, Franklin Lakes, NJ).
DNA probes and labeling
A composite pan-centromeric DNA probe was used to delineate all yeast centromeres (Jin et al., 1998). Two plasmids containing a conserved core fragment of the subtelomeric X and Y' element, respectively (Louis et al., 1994
), were used to probe all yeast telomeres (Gotta et al., 1996
; Trelles-Sticken et al., 1999
). Cosmid probes were used to determine pairing of homologous chromosome regions. The small chromosome III was tagged with a cosmid probe hybridizing to HML near the left telomere of chromosome III (cos m; ATCC 70884). The internal chromosome XI cosmid pEKG151, cos f (Thierry et al., 1995
), mapping to 231.8-264.9 on the left arm of chromosome XI, was used to monitor meiotic pairing at a telomere-distant chromosomal region (Trelles-Sticken et al., 1999
). Probes were labeled either with dig-11-dUTP (Roche Biochem., Mannheim, Germany) or with biotin-14-dCTP (Life Technologies, Gaithersburg, MD) using a nick translation kit according to the supplier's instructions (Life Technologies).
Fluorescence in situ hybridization (FISH)
All preparations were subjected to two color FISH as described previously (Trelles-Sticken et al., 2000). The hybridization solution contained a yeast pan-telomere probe, which delineates all telomeres (2n=32) and a pan-centromeric DNA probe delineating all centromeres in SK1 strains (Jin et al., 1998
; Trelles-Sticken et al., 2000
). Pairing of homologous regions was analyzed by two-color FISH to spread nuclei, using differentially labeled #III and #XI-specific cosmid probes. Immunofluorescent detection of hybrid molecules was carried out with Avidin-FITC (Sigma) and rhodamine-conjugated sheep anti-dig Fab fragments (Roche Biochemicals) (Scherthan et al., 1992
). Prior to microscopic inspection, preparations were embedded in antifade medium (Vector labs, Burlingame, CA) containing 0.5 µg/ml DAPI (4'6-diamidino-2-phenylindole) as a DNA-specific counterstain.
Immunostaining
Immunostaining with a rabbit antiserum (kind gift from S. Roeder, Yale University, CT, USA) against Zip1 transverse filament protein of the yeast synaptonemal complex (Sym et al., 1993) was performed as previously described (Trelles-Sticken et al., 2000
). An anti-rabbit secondary FITC-conjugated antibody was used to identify nuclei with synapsis in progress. Ndj1-HA was stained using a monoclonal anti-HA-tag antibody (Biotec Santa Cruz) and secondary anti-mouse Cy3-conjugated antibodies (Dianova, Hamburg, Germany). Immunostaining against Rap1 was done with a rabbit antiserum (kind gift from S. Schwalader and D. Shore, University of Geneva, Switzerland) and a secondary FITC-conjugated anti-rabbit antibody (Dianova).
Microscopy
Preparations were evaluated using a Zeiss Axioskop 1 epifluorescence microscope equipped with a double-band-pass filter for simultaneous excitation of red and green fluorescence, and single band pass filters for excitation of red, green and blue (Chroma Technologies, Rockingham, VT). Signal patterns in spread nuclei were investigated using a 100x plan-neofluoar lens (Zeiss, Jena, Germany). For each time point and probe combination, fluorescence signal patterns were analyzed in more than 100 nuclei that displayed an undisrupted, homogeneous appearance in the DAPI image. Digital images were obtained using a cooled gray-scale CCD camera (Hamamatsu, Herrsching, Germany) controlled by the ISIS fluorescence image analysis system (MetaSystems, Altlussheim, Germany). Contrast and brightness were adjusted using Adobe Photoshop 6.0 (Adobe) to match the fluorescent image seen in the microscope.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
The initiation of centromere redistribution in the absence of detectable DNA synthesis and the fact that relative kinetics of centromere and telomere dispersion are not strictly fixed (compare wild-type kinetics in Figs 1 and 2) indicate that the centromere and telomere dynamics may be subjected to different controls, possibly connected to premeiotic S phase. To gain a better understanding of this matter a genetic investigation was pursued (see below).
|
While centromere cluster resolution in clb5 cells occurred with kinetics and magnitude similar to that of the wild type (Fig. 2), the dispersion of telomeres was severely limited, with more than half of clb5
nuclei maintaining a vegetative telomere topology throughout the time course. This differential impact of the clb5
mutation on centromere and telomere dynamics was reproducible (see Fig. 5) and indicates that centromere and telomere dispersion are not co-regulated. Centromere dispersion is independent from premeiotic S phase, while telomere dispersion requires a Clb5-dependent function, possibly premeiotic S phase. However, installation of a single meiotic telomere cluster (bouquet formation) still occurred in a fraction of clb5
meiocytes, but with significant delay relative to wild type. This delay was reproducible (see Fig. 5) with the accumulation of late bouquet-like meiocytes suggesting the persistence of this stage in absence of Clb5.
|
Centromere and telomere dynamics are severely affected in set1 cells
To extend our analysis, two other mutants impinging on premeiotic S phase were studied. Ime2 is a meiosis-specific protein kinase that is critical for proper initiation of meiotic progression (Foiani et al., 1996). Accordingly, premeiotic S phase is delayed in ime2
cells (Fig. 3). The consequences of the ime2
mutation on chromosome behavior were similar to that of clb5
with a full dissolution of the centromere cluster, a limited dispersion of vegetative telomere clusters and persistence of bouquet nuclei at late time points (Fig. 3).
|
|
Epistasis relationships between the set1 and clb5
mutations
The differences in centromere and telomere dynamics between set1 and clb5
suggests that, as for premeiotic S phase (Sollier et al., 2004
), Set1 and Clb5 activities are required in different aspects of nuclear reorganization during meiotic prophase. The clb5
set1
double mutant behaves much like set1
cells with a delayed and limited redistribution of centromeres, a severe restriction of vegetative telomere cluster dissolution and a total lack of bouquet formation (Fig. 5). Thus, the set1
defect is upstream of that of clb5
with respect to centromere dispersion and bouquet formation. However, as previously shown (Sollier et al., 2004
), this epistasis relationship does not apply to premeiotic S phase, which never occurs in the case of clb5
set1
(see 1200 minutes on Fig. 5).
Chromosome pairing is defective in set1 meiotic cells
Since meiotic centromere and telomere dynamics were strongly affected in set1 meiocytes, we asked whether the pairing of homologues was also defective. To this end, nuclei were analyzed by FISH with two differentially labeled cosmid probes specific for chromosome III and XI (Trelles-Sticken et al., 2000
). The fraction of paired FISH signals was measured on nuclei prepared from cells used for the meiotic time course experiments presented on Fig. 4 (Fig. 6A, left diagrams). In wild-type meiocytes, the raise of the pairing values for the two probes was similar, increasing from 120 minutes to reach a maximum at 210 minutes. No significant increase of the pairing value occurred along the set1
time course. The same FISH analysis was performed with wild-type, clb5
and clb5
set1
nucleoids from independent time courses (Fig. 6A, right diagrams). It was found that the maximum pairing values for clb5
and clb5
set1
stayed well below that of the wild type.
|
MEC1 inactivation alters telomere dynamics in set1 meiosis
We wondered whether the exacerbated defect in nuclear dynamics seen in set1 was the consequence of the activation of a checkpoint mechanism. As a MEC1-dependent DNA replication checkpoint operating during meiosis has been described (Stuart and Wittenberg, 1998
), we tested the effect of the deletion of SET1 in combination with the mec1-1 mutation. While occurring normally in mec1-1, no premeiotic DNA synthesis was detected in set1
mec1-1 (Fig. 7), consistent with previous data (Sollier et al., 2004
). Meiotic divisions were nearly absent in set1
mec1-1 meiosis, whereas the first meiotic division occurred in the majority of wild-type cells at 420 minutes (not shown). As in set1
meiosis (Fig. 4), centromere cluster resolution was very limited in set1
mec1-1 meiosis (Fig. 7).
|
Telomeric proteins Rap1 and Ndj1 locate to meiotic set1 telomeres
The set1 mutation that resulted in an absence of bouquet formation (this study), was associated with an abnormal telomere structure, apparent notably through the loss of silencing (Corda et al., 1999
; Nislow et al., 1997
). As the meiosis-specific telomeric protein Ndj1 is required for bouquet formation (Trelles-Sticken et al., 2000
), immunolocalization of Ndj1 was performed on wild-type and set1
diploid cells that expressed a HA-tagged version of Ndj1. This was done in the MDY strain background (Conrad et al., 1997
), which displays wild-type nuclear divisions kinetics as well as set1
-associated defects (delay of premeiotic S phase and of prophase I progression, mild sporulation defect) similar to that observed in SK1 (not shown). The appearance of Ndj1-HA immunofluorescence foci was significantly delayed in set1
nuclei (Fig. 8A). Since Ndj1 is required for bouquet formation, this could explain the absence of bouquet formation associated with the loss of Set1. However, even the set1
Ndj1-positive nuclei, which are expected to be able to cluster their telomeres, showed no sign of bouquet formation (Fig. 8 and not shown). To assess that Ndj1 localization is not affected in set1
, we colabeled the XY' telomere repeats using FISH in combination with Ndj1 immunostaining (Fig. 8B). The colocalization or overlap of Ndj1 foci with XY' FISH signals in wild-type nuclei (Trelles-Sticken et al., 2000
) was also observed in set1
meiocytes.
|
The Rap1 protein binds to telomeric sequences and is involved in meiotic telomere structure and function (Kanoh and Ishikawa, 2003). Genetic evidence suggests a role for telomeric Rap1 in S. cerevisiae meiosis (Alexander and Zakian, 2003
), and telomeric localization of Rap1 is necessary for the telomere bouquet in S. pombe meiosis (Chikashige and Hiraoka, 2001
). Co-staining experiments of Ndj1-HA and Rap1 (Fig. 8C) revealed that these proteins colocalize and, except for some rare Rap1-free Ndj1 spots, no discernible difference was found between wild-type and set1
nuclei. This suggests that properly localized telomere proteins require Set1 function to bring about meiotic telomere clustering.
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Telomere dispersion is independent from centromere dispersion
The behavior of clb5 and ime2
nuclei, with normal centromere dispersion in the absence of, or limited, vegetative telomere resolution, fits with the view that the two events are independently controlled. As the two mutations impact on premeiotic S phase, the dispersion of vegetative telomeres could be temporally linked to premeiotic S phase. This goes with the fact that in ime2
the timing of premeiotic S phase and vegetative telomere dispersion is intermediate between those of wild type and clb5
. Moreover, the persistence of vegetative-like telomere clusters in live cells arrested in premeiotic S phase by hydroxyurea suggests that telomere dispersion occurs at the end of, or shortly after, premeiotic S phase (Trelles-Sticken et al., 2005
). This reinforces the idea that premeiotic S phase, or some associated event, is required for telomere dispersion.
Meiotic telomere cluster formation and resolution require Clb5 function
The other important consequence of CLB5 ablation was a delayed appearance of a single and seemingly persistent meiotic telomere cluster. Assuming that this clustering of telomeres corresponds to a genuine bouquet, its detection in unreplicated clb5 meiocytes suggests that meiotic telomere clustering can occur independently of premeiotic S phase. This clustering took place at a time when the fraction of clb5
meiocytes displaying telomere dispersion is limited. This may suggest that a bouquet can form without prior dispersion of telomeres, through the peripheral sliding of vegetative telomere clusters. However, the follow-up of telomere movements in live cells suggest that, at least in wild-type nuclei, telomeres normally disperse before they cluster in the bouquet (Trelles-Sticken et al., 2005
). Since there are never 100% of cells with a vegetative telomere distribution, another possibility is that the bouquet-like topology can arise from the fraction of cells with no apparent vegetative telomere clustering.
The persistence of bouquet nuclei in clb5 could signify that the resolution of meiotic telomere clustering is defective in clb5
. A similar persistence was observed in spo11
and rad50S meiotic time courses (Trelles-Sticken et al., 1999
) and in spo11 Sordaria mutants (Storlazzi et al., 2003
), suggesting that its dissolution requires normal recombination processes. As clb5
is also defective in recombination initiation (Smith et al., 2001
), this fits with the view that the bouquet is normally released after the progression or completion of recombination (Scherthan, 2003
; Storlazzi et al., 2003
). Alternatively, since the bouquet is present in unreplicated clb5
meiocytes and cohesin has been found to be required for the exit from meiotic telomere clustering (Trelles-Sticken et al., 2005
), the accumulation of bouquet nuclei could be due to the lack of appropriately organized cohesin cores along unreplicated chromosomes.
Severe impairment of nuclear dynamics in absence of Set1
The limited delay of premeiotic S phase (Fig. 4) (Sollier et al., 2004) and the good sporulation rate of set1
cells, suggests that the meiotic program is less affected by the absence of Set1 than by the absence of Clb5. As compared to clb5
, nuclear dynamics are more perturbed in set1
meiosis which displays limited centromere dispersion, no clear evidence for vegetative telomere cluster dissolution and absence of bouquet formation. The differences between the two mutants have been summarized in Fig. 9. First, centromere dispersion is limited, as was observed in all strains where the SET1 gene was deleted, whether singly (set1
) or in combination with other mutations (set1
clb5
, set1
mec1-1). A delayed centromere dispersion in sir3
meiosis that is also defective in vegetative telomere metabolism (Trelles-Sticken et al., 2003
) has been correlated to the altered expression of genes involved in vegetative centromere clustering, and a similar mechanism may occur in the absence of Set1.
|
Although one cannot exclude that meiotic telomere clustering could occur in set1 at later times than examined, this would be with a delay largely exceeding that of the premeiotic S phase and normal prophase I (Fig. 4). Moreover, the clustering of telomeres in unreplicated clb5
nuclei suggests that the delay of premeiotic S phase is not responsible for absence of bouquet formation in set1
meiosis. Similarly, the impairment of DSB formation in set1
(Sollier et al., 2004
) is probably not involved, because a bouquet is formed in the spo11
mutant in the absence of meiotic double-strand breaks (Trelles-Sticken et al., 1999
; Storlazzi et al., 2003
). Delayed induction of meiotic middle gene expression (Sollier et al., 2004
) as the cause of bouquet failure seems also unlikely, because meiotic telomere clustering usually precedes the completion of recombination, i.e. before the expression of middle genes. With respect to only a mild defect in sporulation, the set1
mutant is similar to the ndj1
bouquet mutant (Chua and Roeder, 1997
; Conrad et al., 1997
). However, a delayed appearance of Ndj1 at meiotic set1
telomeres seems insufficient to explain the lack of bouquet formation, since telomere clustering was absent in set1
meiocytes that efficiently express well-localized telomeric Rap1 and Ndj1 proteins. Whatever the molecular mechanism whereby Set1 controls meiotic telomere clustering, it could be related to telomeric heterochromatin, as suggested in S. pombe meiosis, in which telomere clustering at the SPB requires the methylation of histone H3 on lysine 9 (Tuzon et al., 2004
). In S. cerevisiae, where there is no H3 lysine 9 methylation, silent heterochromatic DNA at telomeres requires the Sir proteins and a decreased binding of Sir3 at telomeres was observed in set1
(Santos-Rosa et al., 2004
). However, this can certainly not be the cause of the bouquet failure, as Sir3 is dispensable for meiotic telomere clustering (Trelles-Sticken et al., 2003
). This leaves the possibility that Set1-mediated H3-K4 methylation plays a yet unrecognized role in regulating meiotic telomere clustering in budding yeast.
Evidence for a checkpoint controlling telomere dispersion in set1
Among the various defects elicited by the loss of Set1, only the dissolution of vegetative telomere clusters is alleviated by the mec1-1 mutation. This provides an additional corroboration for the independent control of vegetative centromere and telomere cluster dissolution. The temporal relationship between telomere dispersion and premeiotic S phase may signify a functional coupling between the two processes via a checkpoint possibly related to the Mec1-dependent S-M checkpoint that inhibits meiotic M phase in the absence of fully replicated DNA (Stuart and Wittenberg, 1998).
![]() |
Acknowledgments |
---|
![]() |
Footnotes |
---|
Present address: Bundeswehr Institute of Radiobiology, Neuherbergstr. 11, 80937 Munich, Germany
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Alexander, M. K. and Zakian, V. A. (2003). Rap1p telomere association is not required for mitotic stability of a C(3)TA(2) telomere in yeast. EMBO J. 22, 1688-1696.
Borde, V., Goldman, A. S. and Lichten, M. (2000). Direct coupling between meiotic DNA replication and recombination initiation. Science 290, 806-809.
Chikashige, Y. and Hiraoka, Y. (2001). Telomere binding of the Rap1 protein is required for meiosis in fission yeast. Curr. Biol. 11, 1618-1623.[CrossRef][Medline]
Chua, P. R. and Roeder, G. S. (1997). Tam1, a telomere-associated meiotic protein, functions in chromosome synapsis and crossover interference. Genes Dev. 11, 1786-1800.[Abstract]
Conrad, M. N., Dominguez, A. M. and Dresser, M. E. (1997). Ndj1p, a meiotic telomere protein required for normal chromosome synapsis and segregation in yeast. Science 276, 1252-1255.
Corda, Y., Schramke, V., Longhese, M. P., Smokvina, T., Paciotti, V., Brevet, V., Gilson, E. and Géli, V. (1999) Interaction between Set1p and checkpoint protein Mec3p in DNA repair and telomere functions. Nat. Genet. 21, 204-208.[CrossRef][Medline]
Foiani, M., Nadjar-Boger, E., Capone, R., Sagee, S., Hashimshoni, T. and Kassir, Y. (1996). A meiosis-specific protein kinase, Ime2, is required for the correct timing of DNA replication and for spore formation in yeast meiosis. Mol. Gen. Genet. 13, 278-288.[CrossRef]
Goldman, A. S. and Lichten, M. (2000). Restriction of ectopic recombination by interhomolog interactions during Saccharomyces cerevisiae meiosis. Proc. Natl. Acad. Sci. USA 97, 9537-9542.
Gotta, M., Laroche, T., Formenton, A., Maillet, L., Scherthan, H. and Gasser, S. M. (1996). The clustering of telomeres and colocalization with Rap1, Sir3, and Sir4 proteins in wild-type Saccharomyces cerevisiae. J. Cell Biol. 134, 1349-1363.[Abstract]
Hayashi, A., Ogawa, H., Kohno, K., Gasser, S. M. and Hiraoka, Y. (1998). Meiotic behaviours of chromosomes and microtubules in budding yeast: relocalization of centromeres and telomeres during meiotic prophase. Genes Cells 3, 587-601.
Jin, Q., Trelles-Sticken, E., Scherthan, H. and Loidl, J. (1998). Yeast nuclei display prominent centromere clustering that is reduced in nondividing cells and in meiotic prophase. J. Cell Biol. 141, 21-29.
Kane, S. M. and Roth, R. (1974). Carbohydrate metabolism during ascospore development in yeast. J. Bacteriol. 118, 8-14.[Medline]
Kanoh, J. and Ishikawa, F. (2003). Composition and conservation of the telomeric complex. Cell Mol. Life Sci. 60, 2295-2302.[CrossRef][Medline]
Krogan, N. J., Dover, J., Wood, A., Schneider, J., Heidt, J., Boateng, M. A., Dean, K., Ryan, O. W., Golshani, A., Johnston, M. et al. (2003). The Paf1 complex is required for histone H3 methylation by COMPASS and Dot1p: linking transcriptional elongation to histone methylation. Mol. Cell 11, 721-729.[CrossRef][Medline]
Loidl, J. (1990). The initiation of meiotic chromosome pairing: the cytological view. Genome 33, 759-778.[Medline]
Louis, E. J., Naumova, E. S., Lee, A., Naumov, G. and Haber, J. E. (1994). The chromosome end in yeast: its mosaic nature and influence on recombinational dynamics. Genetics 136, 789-802.
Miller, T., Krogan, N. J., Dover, J., Erdjument-Bromage, H., Tempst, P., Johnston, M., Greenblatt, J. F. and Shilatifard, A. (2001). COMPASS: a complex of proteins associated with a trithorax-related SET domain protein. Proc. Natl. Acad. Sci. USA 98, 12902-12907.
Nagy, P. L., Griesenbeck, J., Kornberg, R. D. and Cleary, M. L. (2002). A trithorax-group complex purified from Saccharomyces cerevisiae is required for methylation of histone H3. Proc. Natl. Acad. Sci. USA 99, 90-94.
Ng, H. H., Robert, F., Young, R. A. and Struhl, K. (2003). Targeted recruitment of Set1 histone methylase by elongating Pol II provides a localized mark and memory of recent transcriptional activity. Mol. Cell 11, 709-719.[CrossRef][Medline]
Nislow, C., Ray, E. and Pillus, L. (1997). SET1, a yeast member of the trithorax family, functions in transcriptional silencing and diverse cellular processes. Mol. Biol. Cell 8, 2421-2436.
Niwa, O., Shimanuki, M. and Miki, F. (2000). Telomere-led bouquet formation facilitates homologous chromosome pairing and restricts ectopic interaction in fission yeast meiosis. EMBO J. 19, 3831-3840.
Padmore, R., Cao, L. and Kleckner, N. (1991). Temporal comparison of recombination and synaptonemal complex formation during meiosis in S. cerevisiae. Cell 66, 1239-1256.[CrossRef][Medline]
Petronczki, M., Siomos, M. F. and Nasmyth, K. (2003). Un menage a quatre: the molecular biology of chromosome segregation in meiosis. Cell 112, 423-440.[CrossRef][Medline]
Rockmill, B. and Roeder, G. S. (1998). Telomere-mediated chromosome pairing during meiosis in budding yeast. Genes Dev. 12, 2574-2586.
Roeder, G. S. (1997). Meiotic chromosomes: it takes two to tango. Genes Dev. 11, 2600-2621.
Roguev, A., Schaft, D., Shevchenko, A., Pijnappel, W. W., Wilm, M., Aasland, R. and Stewart, A. F. (2001). The Saccharomyces cerevisiae Set1 complex includes an Ash2 homologue and methylates histone 3 lysine 4. EMBO J. 20, 7137-7148.
Roth, R. and Halvorson, H. O. (1969). Sporulation of yeast harvested during logarithmic growth. J. Bacteriol. 98, 831-832.[Medline]
Santos-Rosa, H., Bannister, A. J., Dehe, P. M., Géli, V. and Kouzarides, T. (2004). Methylation of H3 lysine 4 at euchromatin promotes Sir3p association with heterochromatin. J. Biol. Chem. 279, 47506-47512.
Scherthan, H. (2001). A bouquet makes ends meet. Nat. Rev. Mol. Cell. Biol. 2, 621-627.[CrossRef][Medline]
Scherthan, H. (2003). Knockout mice provide novel insights into meiotic chromosome and telomere dynamics. Cytogenet. Genome Res. 103, 235-244.[CrossRef][Medline]
Scherthan, H., Kohler, M., Vogt, P., von Malsch, K. and Schweizer, D. (1992). Chromosomal in situ hybridization with double-labeled DNA: signal amplification at the probe level. Cytogenet. Cell Genet. 60, 4-7.[Medline]
Schramke, V., Neecke, H., Brevet, V., Corda, Y., Lucchini, G., Longhese, M. P., Gilson, E. and Géli, V. (2001). The set1Delta mutation unveils a novel signaling pathway relayed by the Rad53-dependent hyperphosphorylation of replication protein A that leads to transcriptional activation of repair genes. Genes Dev. 15, 1845-1858.
Smith, K. N., Penkner, A., Ohta, K., Klein, F. and Nicolas, A. (2001). B-type cyclins CLB5 and CLB6 control the initiation of recombination and synaptonemal complex formation in yeast meiosis. Curr. Biol. 11, 88-97.[CrossRef][Medline]
Sollier, J., Lin, W., Soustelle, C., Suhre, K., Nicolas, A., Géli, V. and de La Roche Saint-André, C. (2004). Set1 is required for meiotic S-phase onset, double-strand break formation and middle gene expression. EMBO J. 23, 1957-1967.
Storlazzi, A., Tesse, S., Gargano, S., James, F., Kleckner, N. and Zickler, D. (2003). Meiotic double-strand breaks at the interface of chromosome movement, chromosome remodeling, and reductional division Genes Dev. 17, 2675-2687.
Stuart, D. and Wittenberg, C. (1998). CLB5 and CLB6 are required for premeiotic DNA replication and activation of the meiotic S/M checkpoint. Genes Dev. 12, 2698-2710.
Sym, M. and Roeder, G. S. (1995). Zip1-induced changes in synaptonemal complex structure and polycomplex assembly. J. Cell Biol. 128, 455-466.[Abstract]
Sym, M., Engebrecht, J. A. and Roeder, G. S. (1993). ZIP1 is a synaptonemal complex protein required for meiotic chromosome synapsis. Cell 72, 365-378.[CrossRef][Medline]
Thierry, A., Gaillon, L., Galibert, F. and Dujon, B. (1995). Construction of a complete genomic library of Saccharomyces cerevisiae and physical mapping of chromosome XI at 3.7 kb resolution. Yeast 11, 121-135.[Medline]
Trelles-Sticken, E., Loidl, J. and Scherthan, H. (1999). Bouquet formation in budding yeast: initiation of recombination is not required for meiotic telomere clustering. J. Cell Sci. 112, 651-658.
Trelles-Sticken, E., Dresser, M. E. and Scherthan, H. (2000). Meiotic telomere protein Ndj1p is required for meiosis-specific telomere distribution, bouquet formation and efficient homologue pairing. J. Cell Biol. 151, 95-106.
Trelles-Sticken, E., Loidl, J. and Scherthan, H. (2003). Increased ploidy and KAR3 and SIR3 disruption alter the dynamics of meiotic chromosomes and telomeres. J. Cell Sci. 116, 2431-2442.
Trelles-Sticken, E., Adelfalk, C., Loidl, J. and Scherthan, H. (2005). Meiotic telomere clustering requires actin for its formation and cohesin for its resolution. J. Cell Biol. 170, 213-223.
Tuzon, C. T., Borgstrom, B., Weilguny, D., Egel, R., Cooper, J. P. and Nielsen, O. (2004). The fission yeast heterochromatin protein Rik1 is required for telomere clustering during meiosis. J. Cell Biol. 165, 759-765.
von Wettstein, D. (1984). The synaptonemal complex and genetic segregation. Symp. Soc. Exp. Biol. 38, 195-231.[Medline]
Zickler, D. and Kleckner, N. (1998). The leptotene-zygotene transition of meiosis. Annu. Rev. Genet. 32, 619-697.[CrossRef][Medline]