Project description:It is generally believed that silent chromatin is condensed and transcriptionally active chromatin is decondensed. However, little is known about the relationship between condensation levels and gene expression. Here we report condensation levels of interphase chromatin in the fission yeast Schizosaccharomyces pombe examined by super-resolution fluorescence microscopy. Unexpectedly, silent chromatin was observed to be less condensed than the euchromatin. Furthermore, the telomeric silent regions were flanked by highly condensed chromatin bodies, or “knobs”. Knob regions span approximately 50 kb of sequence devoid of methylated histones. Knob condensation was independent of HP1 homolog Swi6 and other gene silencing factors. Disruption of methylation at lysine 36 of histone H3 (H3K36) eliminated knob formation and gene repression at the subtelomeric and adjacent knob regions. Thus, epigenetic marks atH3K36 play crucial roles in the formation of a unique chromatin structure and in gene regulation at those regions in S. pombe.
Project description:A chromosome is composed of structurally and functionally distinct domains. However, the molecular mechanisms underlying the formation of chromatin structure and the function of subtelomeres, the telomere-adjacent regions, remain obscure. Here we report the roles of the conserved centromeric protein Shugoshin 2 (Sgo2) in defining chromatin structure and functions of the subtelomeres in the fission yeast Schizosaccharomyces pombe. We show that Sgo2 localizes at the subtelomeres preferentially during G2 phase and is essential for the formation of a highly condensed subtelomeric chromatin body 'knob'. Furthermore, the absence of Sgo2 leads to the derepression of the subtelomeric genes and premature DNA replication at the subtelomeric late origins. Thus, the subtelomeric specialized chromatin domain organized by Sgo2 represses both transcription and replication to ensure proper gene expression and replication timing.
Project description:Phospho-site mutants of the RNA Polymerase II C-terminal domain alter subtelomeric gene expression and chromatin modification state in fission yeast
Project description:We report the high-throughput profiling of H3K9me2 in fission yeast Schizosaccharomyces pombe. By obtaining 1-10 ng immunoprecipitated DNA, we generated genome-wide H3K9me2 maps in single deletions of the selected chromatin modulating genes, histone H3 mutants and ccp1Δepe1Δ double mutant in fission yeast. We find that the subtelomeric heterochromatin distribution is highly variable under different genetic perturbations and small heterochromatin islands are formed at clr4 and clr2 loci in ccp1Δepe1Δ.
