Mechanisms of RNA Mediated Silencing in S. pombePublic Deposited
Mechanisms of RNA Mediated Silencing in S. pombe Christina A. Lawrence Heterochromatin of eukaryotic genomes has classically been defined as condensed chromatin that is repressive to transcription and typically resides at highly repetitive regions of the genome. Genetic and molecular analyses have demonstrated that these regions are essential for genome integrity and stability. The fission yeast, S. pombe has emerged as a powerful system to understand the mechanisms of heterochromatin assembly. The conserved RNA interference pathway has been shown to silence regions of the genome through post-transcriptional and transcriptional gene silencing mechanisms. RNAi directs transcriptional silencing via the recruitment of heterochromatin formation at the centromeres, telomeres, and mating-type region of S. pombe. Assembly of heterochromatin domains has been postulated to occur in discrete nucleation and spreading (from nucleation sites) phases that requires histone modifiers as well as RNAi. However, due to the highly repetitive architecture of heterochromatic regions, defining the mechanisms necessary for initiating heterochromatin nucleation has proven problematic. We therefore aimed to investigate the mechanism of how heterochromatin is targeted to specific loci in order to establish a silent domain. We also sought to determine potential differences in the regulation of the various repeats within the heterochromatin regions of S. pombe.