H3K9me-Independent Gene Silencing in Fission Yeast Heterochromatin by Clr5 and Histone Deacetylases
Figure 1
Prominant role of histone deacetylation in the repression of mat2-P.
(A) Schematic representation of the mating-type region. The region between IR-L (inverted repeat left) and IR-R (inverted repeat right) is heterochromatic. Binding sites for the Ste11 transcription factor within the mating-type cassettes are indicated by brown arrows; a binding site for Atf1 in REIII is indicated by a green arrow. A second Atf1 binding site located between cenH and REIII is not represented. The smt-0 mutation prevents switching of the mat1-M cassette allowing the expression of mat2-P to be assayed by iodine staining of colonies or by RT-PCR. Primers used for RT-PCR analysis are indicated by arrowheads below mat2-P and mat3-M. REII: repressor element II; REIII: repressor element III; cenH: centromere homology. (B) Iodine staining of wild-type (PG1789), clr4Δ (SPK450), clr3Δ (PG3564), swi6-115 (SPK29), clr6-1 (SPK467) and clr3Δ clr6-1 (PG3577) strains propagated on MSA sporulation plates. Dark iodine staining is due to haploid meiosis and reflects mat2-P expression. (C) Assay of mat2-Pc transcript levels by RT-PCR. RNA was prepared from strains induced to enter the meiotic program by 5 hours of nitrogen starvation in PM-nitrogen liquid medium. The strains are as in B.