Previous Article | Next Article ![]()
Mol. Cell. Biol., 07 1995, 3608-3617, Vol 15, No. 7
H Laman, D Balderes and D Shore
Previous studies have indicated that mutation of RAP1 (rap1s) or of the
HMR-E silencer ARS consensus element leads to metastable repression of HMR.
A number of extragenic suppressor mutations (sds, suppressors of defective
silencing) that increase the fraction of repressed cells in rap1s hmr delta
A strains have been identified. Here we report the cloning of three SDS
genes. SDS11 is identical to SWI6, a transcriptional regulator of genes
required for DNA replication and of cyclin genes. SDS12 is identical to
RNR1, which encodes a subunit of ribonucleotide reductase. SDS15 is
identical to CIN8, whose product is required for spindle formation. We
propose that mutations in these genes improve the establishment of
silencing by interfering with normal cell cycle progression. In support of
this idea, we show that exposure to hydroxyurea, which increases the length
of S phase, also restores silencing in rap1s hmr delta A strains. Mutations
in different cyclin genes (CLN3, CLB5, and CLB2) and two cell cycle
transcriptional regulators (SWI4 and MBP1) also suppress the silencing
defect at HMR. The effect of these cell cycle regulators is not specific to
the rap1s or hmr delta A mutation, since swi6, swi4, and clb5 mutations
also suppress mutations in SIR1, another gene implicated in the
establishment of silencing. Several mutations also improve the efficiency
of telomeric silencing in wild-type strains, further demonstrating that
disturbance of the cell cycle has a general effect on position effect
repression in Saccharomyces cerevisiae. We suggest several possible models
to explain this phenomenon.
Copyright © 1995, American Society for Microbiology
Disturbance of normal cell cycle progression enhances the establishment of transcriptional silencing in Saccharomyces cerevisiae
Department of Microbiology, College of Physicians & Surgeons of Columbia University, New York, New York 10032, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»