Project description:We identified lysine 37 of histone H2B as a novel site of histone lysine methylation in budding yeast. Microarray analysis was performed to determine global changes in gene expression upon mutation of this lysine residue to a unmodifiable form. Histones were acid-extracted from asynchronously grown yeast expressing wild-type H2B or H2B harboring a K37A mutation.
Project description:Nucleosome assembly in vivo requires assembly factors, such as histone chaperones, to bind to histones and mediate their deposition onto DNA. In yeast, the essential histone chaperone FACT (FAcilitates Chromatin Transcription) functions in nucleosome assembly and H2A-H2B deposition during transcription elongation and DNA replication. Recent studies have identified candidate histone residues that mediate FACT binding to histones, but it is not known which histone residues are important for FACT to deposit histones onto DNA during nucleosome assembly. In this study, we report that the histone H2B repression (HBR) domain within the H2B N-terminal tail is important for histone deposition by FACT. Deletion of the HBR domain causes significant defects in histone occupancy in the yeast genome, particularly at HBR-repressed genes, and a pronounced increase in H2A-H2B dimers that remain bound to FACT in vivo. Moreover, the HBR domain is required for purified FACT to efficiently assemble recombinant nucleosomes in vitro. We propose that the interaction between the highly basic HBR domain and DNA plays an important role in stabilizing the nascent nucleosome during the process of histone H2A-H2B deposition by FACT. 6 samples, 2 inputs and 4 ChIP samples for histone H2B (2 for wild-type and 2 for an H2B â30-37 mutant)
Project description:Effect of FLO8 or MSS11 deletion and -overexpression on yeast transcript profiles compared to wild type in laboratory yeast strains Σ1278b and S288c.
Project description:Histones are the main components in chromatin organization, and the protein levels of histones significantly affect chromatin assembly. However, how the protein levels of histones are regulated, especially whether and how histones are degraded, is largely unclear. Here, we found that histone H2B is mainly degraded through the proteasome mediated pathway, and the lysine 120 site of H2B is essential for the K48-linked polyubiquitination and protein degradation of H2B. Moreover, our results further indicated that the degradation-impaired H2BK120R mutant shows an increased nucleolus localization, and inhibition of the proteasome results in an elevated nucleolus distribution of wild-type H2B, which is similar to that of H2BK120R mutants. More importantly, our in vitro data showed that only the nucleolus fractions can ubiquitinate and degrade the purified H2B, suggesting that the nucleolus, in addition to its canonical roles in the regulation of ribosome genesis and protein translation, is likely associated with H2B protein degradation. Therefore, these findings revealed a novel mechanism for the regulation of H2B protein degradation in which a nucleolus associated proteasome pathway is involved.