Importance of the Clr2 protein in heterochromatin formation in the fission yeast Schizosaccharomyces pombe

Sammanfattning: Epigenetics is an area of biology that studies heritable changes in gene ex- pression without any change in the DNA sequence. The most studied epige- netic mechanisms are DNA methylation, RNA interference and histone mod- ifications. There are over 130 different modifications that can be attached to histones, and the most commonly studied are methylation, acetylation, phos- phorylation, sumoylation and ubiquitination. The modifications, spread out through the genome, form the histone code, which recruits transcription fac- tors and modifies the accessibility of the DNA, which results in either active or silenced transcription. The silenced form of chromatin is known as heter- ochromatin and is usually found in regions of the chromosome that need to be highly regulated. To study epigenetics, the model organism Schizosac- charomyces pombe is used widely used. S. pombe is a single cell, rod shaped, fission yeast. The simplicity of S. pombe and its similarities to high- er eukaryotes makes it a good model organism for studying epigenetics. We find that, when mutating evolutionary conserved amino acids in the Clr2 protein, which is involved in heterochromatin formation in S. pombe, there is a change in silencing in different heterochromatic regions. When constructs of Clr2 with the BAH domain deleted are overexpressed, there is an increase in silencing in the central core centromere of chromosome II of S. pombe.