A Key Role for Chd1 in Histone H3 Dynamics at the 3' Ends of Long Genes in Yeast (Rpb3 to input)

Chd proteins are ATP-dependent chromatin remodeling enzymes implicated in biological functions from transcriptional elongation to control of pluripotency. Here, we examine roles of Chd1 in replication- independent dynamics of histone H3 in yeast. Using genome-wide ChIP on chip analysis, we find that Chd1 influences histone turnover at the 5’ and 3’ ends of genes, accelerating H3 replacement at the 5’ ends of genes while protecting the 3’ ends of genes from excessive H3 turnover. Although consistent with a direct role for Chd1 in exchange, these results may indicate that Chd1 stabilizes nucleosomes perturbed by transcription. Curiously, we observe a strong effect of gene length on Chd1’s effects on H3 turnover. Finally, we show that Chd1 also affects histone H3K4 and H3K36 methylation patterns over genes, likely as a consequence of its effects on histone replacement. In control experiments, we measure effects of deletion of CHD1 on RNA polymerase II distribution across the genome and on gene expression. We also examine the effect of deleting the TOP1 gene, alone and in combination with deletion of CHD1, on histone replacement. Taken together, our results emphasize a role for Chd1 in histone replacement in both budding yeast and Drosophila, and surprisingly show that the major effects of Chd1 on turnover occur at the 3’ ends of genes. ChIP on chip experiments, compare IP to input, with dye-flips, comparing distribution of RNA polymerase II in chd1 deletion to wild type cells.