The chromatin structure of Fission yeast centromeres is regulated epigenetically. In the central core domain, the histone H3 variant Cnp1(CENP-A) plays a key role. In the flanking heterochromatin domain, histones are kept underacetylated by the histone deacetylases (HDACs) Clr3, Clr6 and Sir2, and methylated by Clr4 methyltransferase (HMTase) to create a specific binding site for the Swi6 protein. Swi6 then directly mediates cohesin binding to the centromeric heterochromatin. Recognizes and binds histone H3 tails methylated at Lys-9, leading to epigenetic repression. Involved in the repression of the silent mating-type loci MAT2 and MAT3. May compact MAT2/3 into a heterochromatin-like conformation which represses the transcription of these silent cassettes.
Swi6 interacts with histone H3 methylated at Lys-9 and with the cohesin subunit psc3.
Swi6 associates with Swi4 to activate HO and many other late G1-specific transcripts in budding yeast. In contrast, histone H3 methylated at Lys9 and its interacting protein Swi6/HP1, which define heterochromatin, coated extended domains associated with a variety of repeat elements and small islands corresponding to meiotic genes. Contains two chromo domains.
Sadeghi L et al. The Paf1 complex factors Leo1 and Paf1 promote local histone turnover to modulate chromatin states in fission yeast. EMBO Rep16:1673-87 (2015).
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