Study On The Role Of Histone H2B Ubiquitinationin Melosis

Histones are subject to multiple different types of posttranslational modifications,including acetylation, phosphorylation, methylation, ubiquitination and glycosylation.These different modifications play important roles in chromatin structureremodeling,transcriptional regulation and DNA damage repair. Histone H2Bubiquintylation involves lots of protein complexes including Rad6, Bre1 and Lge1 inbudding yeast. H2B deubiquintylation involves mainly Ubp8 and Ubp10 in buddingyeast. Lge1 can promote the recruitment of Bre1 and inhibit recruitment of Ubp8.H2B ubiquintylation has been shown to be important for gamete formation andmeiosis. However, the mechanism of how H2B ubiquintylation affects meiosis is stillunknown. In this thesis, I focused on studying the role of Bre1, Lge1, Ubp8 andUbp10 in yeast sporulation. The main findings include:1. I determined the subcellular localization of Bre1 and Lge1 by using yeast linesexpressing GFP fusion proteins. Bre1 and Lge1 mainly localized in nuleus.2. I found that knockout of Bre1 and Lge1 can significantly decrease the yeastsporulation efficiency. However, a double mutant of Ubp8 and Ubp10 did notsignificantly influence the yeast sporulation efficiency.3. I constructed a H2B K123R mutant yeast strain to study the role of H2Bubiquintylation in meiosis.4. I constructed a Rnf20 (homolog of Bre1 in mammals) conditional knockout vectorin mice and obtained F1 mosaic mice successfully, which can be mated to getgermline transmitted F2 and homozygous floxed F3 mice. In the future, we canselectively knockout Rnf20 in reproductive organs such as ovary and testis tostudy the role of Rnf20 in gametogenesis.As a summary, I made substantial progress on studying the role of H2Bubiquintylation in meiosis in budding yeast and mice. Further studies are needed tocompletely figure out how H2B ubiquintylation affect meiosis.