Project description:We report genome wide mapping of the histone variant H2A.Z during G0/G1 and mitosis in T24 bladder cancer cells. The results show that the broad enrichment pattern of H2A.Z near transcription start sites of active genes is maintained during mitosis. Furthermore, using H2A.Z localization to visualize nucleosome positioning near the start site, we see that the +1 nucleosome of active genes shifts upstream to occupy the transcription start sites during mitosis and the nucleosome depleted region is shortened. H2A.Z is also maintained on the -2 nucleosome which also shifts towrds the transcription start site during mitosis, further contributing to the shorteneing of the nucleosome depleted region.
Project description:We report genome wide mapping of the histone variant H2A.Z during G0/G1 and mitosis in T24 bladder cancer cells. The results show that the broad enrichment pattern of H2A.Z near transcription start sites of active genes is maintained during mitosis. Furthermore, using H2A.Z localization to visualize nucleosome positioning near the start site, we see that the +1 nucleosome of active genes shifts upstream to occupy the transcription start sites during mitosis and the nucleosome depleted region is shortened. H2A.Z is also maintained on the -2 nucleosome which also shifts towrds the transcription start site during mitosis, further contributing to the shorteneing of the nucleosome depleted region. Examination of H2A.Z duing G0/G1 and mitosis in bladder cancer cells
Project description:Nucleosome structure directly influences gene transcription. However, the function of each histone residue remains largely unknown. Here we profiled gene expression changes upon the mutation of individual residues of histone H3 and H4. Histone residues grouped by expression change similarity displayed overall structural relevance. This regulatory functional map of the core histones led to novel findings. First, the residues specific to each histone family tend to be more influential than those commonly found among different histones. Second, unlike histone acetylations, H3K4 trimethylation does not appear to be prerequisite for gene activation. Third, H3Q5 has been newly identified for its putative interactions with many chromatin regulators for transcription control. Lastly, the nucleosome lateral surface seems to play a key role through interactions with the surrounding DNA. Remarkably, we discovered a novel role for H3K56 in chromatin dynamics. The deletion of this residue, but not the alteration of acetylation states, caused a genome-wide decrease in nucleosome mobility and stabilized nucleosome positioning near transcription start and end sites. Occupying the DNA entry/exit site, H3K56 is thought to modulate nucleosome sliding along DNA. Taken together, genomics approaches such as microarray and deep sequencing prove valuable for mapping the function of histone residues. Performing Mnase-seq for six histone mutants and two wild-types in Saccharomyces cerevisiae
Project description:Numerous nucleosome remodeling enzymes tightly regulate nucleosome positions in eukaryotic cells. Transcription and statistical positioning of nucleosomes may also contribute to proper nucleosome organization. Individual contributions remain controversial due to strong redundancy of processes acting on the nucleosome landscape. By incisive yeast genome engineering we radically decreased their redundancy. We find the transcriptional machinery to be disruptive of evenly spaced nucleosomes, and proper nucleosome density critical for their biogenesis. INO80 spaces nucleosomes in vivo and positions the first nucleosome covering genes. It requires its Arp8 and Ies2 subunits, but unexpectedly not the Nhp10 module, for spacing. Whereas H2A.Z stimulates INO80 in vitro, its presence is dispensable for INO80 +1 positioning function in vivo. DNA damage, recombination and transposon integration assays suggest that evenly spaced nucleosomes protect cells against genotoxic stress. We derive a unifying model of the biogenesis of the nucleosome landscape and suggest that it evolved not only to regulate but also to protect the genome.