Regulation of Budding Yeast CENP-A levels Prevents Misincorporation at Promoter Nucleosomes and Transcriptional Defects

The exclusive localization of the histone h3 variant cenp-a to centromeres is essential for accurate chromosome segregation. ubiquitin-mediated proteolysis helps to ensure that cenp-a does not mislocalize to euchromatin,which can lead to genomic instability. consistent with this,overexpression of the budding yeast cenp-acse4is lethal in cells lacking psh1,the e3 ubiquitin ligase that targets cenp-acse4for degradation. to identify additional mechanisms that prevent cenp-acse4misincorporation and lethality,we analyzed the genome-wide mislocalization pattern of overexpressed cenp-acse4in the presence and absence of psh1 by chromatin immunoprecipitation followed by high throughput sequencing. we found that ectopic cenp-acse4is enriched at promoters that contain histone h2a.zhtz1nucleosomes,but that h2a.zhtz1is not required for cenp-acse4mislocalization. instead,the ino80 complex,which removes h2a.zhtz1from nucleosomes,promotes the ectopic deposition of cenp-acse4. transcriptional profiling revealed gene expression changes in the psh1δ cells overexpressing cenp-acse4. the down-regulated genes are enriched for cenp-acse4mislocalization to promoters,while the up-regulated genes correlate with those that are also transcriptionally up-regulated in an htz1δ strain. together,these data show that regulating centromeric nucleosome localization is not only critical for maintaining centromere function,but also for ensuring accurate promoter function and transcriptional regulation. © 2016 hildebrand,biggins.