A poorly understood facet of meiotic gene regulation is how
transcriptional repression is reestablished following normal in-
duction. Several ﬁndings in the present and previous studies
argue that the system controlling mitotic repression of the
EMG is different than that installed in meiotic cells. First,
Ume6p is not required for reestablishing repression. This is
demonstrated in several ways. We have previously shown that
Ume6p destruction is required for EMG induction (16). How-
ever, Ume6p levels do not return until spore wall assembly,
which occurs after EMG repression is reestablished. Consis-
tent with this conclusion, we demonstrate that PAH2, the
Ume6p interaction domain, is not required for reestablishing
repression. In addition, other factors that mediate EMG re-
pression in vegetative cells are not required for reestablishing
repression. For example, loss of Ume1p (17), cyclin C (Ssn3p)
(8), or Cdk8p (Ssn8p) (33) activity does not effect this process.
We have not directly tested the role of Rpd3p in this regula-
tion, but the requirement of PAH3, the HDAC-interacting
domain, strongly suggests this possibility. These results indi-
cate that only Sin3p and Rpd3p are required for EMG repres-
sion before and after induction. Furthermore, Sin3p utilizes
PAH2 and PAH3 for vegetative repression but PAH3 and
PAH4 for meiotic repression.
How does Sin3p mediate meiotic repression? Most studies
to date in several systems indicate that Sin3p is recruited to the
promoter by a DNA binding factor. For EMG vegetative re-
pression, Ume6p serves this role. However, Ume6p is not
involved in Sin3p-dependent meiotic repression. One possibil-
ity is that Sin3p jumps to one of the other two DNA binding
factors identiﬁed in this report that recognize the ARE or T4C
sequences (see Fig. 7, bottom right). In support of this model,
EMSA analysis found that complexes C5 and C6 are main-
tained throughout meiosis and spore formation (data not
shown). An alternative possibility is that Sin3p does not utilize
a transcription factor to reestablish repression (Fig. 7, bottom
left). For example, chromatin immunoprecipitation studies re-
vealed that the human Sin3 associates with additional loci
independent of known DNA binding factors following myo-
genic differentiation (35). In addition, the Sin3p-Rpd3p com-
plex can stably associate with chromatin in vitro (36). A careful
mapping of Sin3p-Rpd3p locations before and after induction,
as well as the identiﬁcation of the ARE and/or T4C binding
proteins, will be necessary to answer this question.
Why employ two systems to repress EMG expression? Dur-
ing vegetative growth, the meiotic genes are silent but must be
ready to be activated upon the correct environmental cues.
However, following the induction of these genes during meio-
sis, the cell completes the program and the haploid nuclei are
encapsulated into spores. These spores can remain dormant
for extended periods without losing viability. Therefore, a
mechanism that maintains repression in spores has to be sturdy
but perhaps not as responsive. Then, as the spore germinates
and returns to mitotic cell division, the responsive, PAH2-
dependent system would be installed at the early meiotic pro-
moters. Understanding the nature of this system may shed light
onto gene silencing that occurs in terminally differentiated cells
in higher systems.
We thank E. Winter, K. Cooper, and M. Henry for helpful discus-
sions and critical readings of the manuscript. We thank D. Stillman for
the PAH deletion series and valuable discussion throughout the course
of this work.
This work was supported by public health service grants GM-086788
and CA-099003 from the General Medicine and National Cancer In-
1. Arcangioli, B., and B. Lescure. 1985. Identiﬁcation of proteins involved in
the regulation of yeast iso-1-cytochrome C expression by oxygen. EMBO
2. Ayer, D. E., Q. A. Lawrence, and R. N. Eisenman. 1995. Mad-Max transcrip-
tional repression is mediated by ternary complex formation with mammalian
homologs of yeast repressor Sin3. Cell 80:767–776.
3. Bowdish, K. S., and A. P. Mitchell. 1993. Bipartite structure of an early
meiotic upstream activation sequence from Saccharomyces cerevisiae. Mol.
Cell. Biol. 13:2172–2181.
4. Braunstein, M., A. B. Rose, S. G. Holmes, C. D. Allis, and J. R. Broach. 1993.
Transcriptional silencing in yeast is associated with reduced nucleosome
acetylation. Genes Dev. 7:592–604.
5. Buckingham, L. E., H.-T. Wang, R. T. Elder, R. M. McCarroll, M. R. Slater,
and R. E. Esposito. 1990. Nucleotide sequence and promoter analysis of
SPO13, a meiosis-speciﬁc gene of Saccharomyces cerevisiae. Proc. Natl. Acad.
Sci. U. S. A. 87:9406–9410.
6. Carrozza, M., L. Florens, S. Swanson, W. Shia, S. Anderson, J. Yates, M.
Washburn, and J. Workman. 2005. Stable incorporation of sequence speciﬁc
repressors Ash1 and Ume6 into the Rpd3L complex. Biochim. Biophys. Acta
1731:77–87; discussion 75–76.
7. Chu, S., J. DeRisi, M. Eisen, J. Mulholland, D. Botstein, P. O. Brown, and
I. Herskowitz. 1998. The transcriptional program of sporulation in budding
yeast. Science 282:699–705.
8. Cooper, K. F., and R. Strich. 2002. Saccharomyces cerevisiae C-type cyclin
UME3/SRB11 is required for efﬁcient induction and execution of meiotic
development. Eukaryot. Cell 1:67–76.
9. Gietz, R. D., and A. Sugino. 1988. Escherichia coli shuttle vectors constructed
with in vitro mutagenized yeast genes lacking six-base-pair restriction sites.
10. Goldmark, J. P., T. G. Fazzio, P. W. Estep, G. M. Church, and T. Tsukiyama.
2000. The Isw2 chromatin remodeling complex represses early meiotic genes
upon recruitment by Ume6p. Cell 103:423–433.
11. Hepworth, S. R., H. Friesen, and J. Segall. 1998. NDT80 and the meiotic
recombination checkpoint regulate expression of middle sporulation-speciﬁc
genes in Saccharomyces cerevisiae. Mol. Cell. Biol. 18:5750–5761.
12. Honigberg, S. M., R. M. McCarroll, and R. E. Esposito. 1993. Regulatory
mechanisms in meiosis. Curr. Opin. Cell Biol. 5:219–225.
13. Kadosh, D., and K. Struhl. 1997. Repression by Ume6 involves recruitment
of a complex containing Sin3 corepressor and Rpd3 histone deacetylase to
target promoters. Cell 89:365–371.
14. Kassir, Y., D. Granot, and G. Simchen. 1988. IME1, a positive regulator of
meiosis in S. cerevisiae. Cell 52:853–862.
FIG. 7. Model for Sin3p-dependent mitotic (top) and two potential
meiotic (bottom) repression systems. During vegetative growth, Sin3p
bridges Rpd3p to Ume6p, utilizing PAH3 and PAH2, respectively.
Meiotic repression occurs in the absence of Ume6p and requires
PAH3 and PAH4 by associating to the promoter in a transcription
factor-independent (left) or -dependent (right) fashion.
OL. 9, 2010 Sin3p REGULATES TRANSIENT TRANSCRIPTION 1843