Practice question

Heterochromatin hallmark histone H3 lysine 9 methylation catalyzed by evolutionary conserved suppressor of variegation 3-9 family enzyme Clr4 in Schizosaccharomyces pombe, mammalian SUV39H1 and SUV39H2 orthologs. Clr4 within CLRC complex comprising Cul4 ubiquitin ligase scaffold, Rik1, Raf1, Raf2, Stc1 adapter transfers methyl group from donor S-adenosylmethionine to H3K9 epsilon amino group producing mono di trimethyl states. H3K9me2 and H3K9me3 recognized by chromodomain proteins Swi6, Chp2, Chp1 aromatic cage mediating chromatin compaction and spreading. Clr4 recruitment requires deacetylated histones and RITS tethering, establishing heterochromatin at centromeres, telomeres, mating type locus crucial for chromosome segregation, sister chromatid cohesion, and genome stability.