Elucidating Epigenetic Readers of H3T45ph in S. cerevisiae

Abstract

The phosphorylation of histone H3 threonine 45 (H3T45ph) in S. cerevisiae and mammalian cells occurs at the N‐terminal alpha‐helix and aligns at the precise location of DNA points of entry and exit on the nucleosome. The phosphorylation peaks during S‐phase and is mediated by the DNA replication kinase Cdc7, which is dependent on forming a complex with Dbf4 to phosphorylate the residue. Loss of T45ph leads to greater sensitivity to replicative stress, but it is not required for cell survival. ChIP‐seq was used to identify the genomic sites of H3T45ph in asynchronous and hydroxyurea (HU) treated cells and RT‐qPCR to determine the mark's influence on transcription. These studies revealed that H3T45ph is located at both origins of replication and at the sites of highly transcribed genes responsible for protein synthesis and glycolysis. Here we aim to elucidate the reader(s) of the H3T45ph mark to aid in understanding the possible roles H3T45ph may play in regulating chromatin structure, the recruitment of transcription factors, or the recruitment of the DNA replication or repair machinery. Our research supports the identification of readers of the mark, which perform a wide variety of functions and are classically associated with DNA damage repair pathways and stabilizing stalled replication forks, as well as differentially regulating rapamycin‐mediated transcription. We hypothesize that these factors act as transcription factors that regulate ribosome biogenesis and cell growth, as well as aid in DNA replication. We speculate this pathway is crucial for efficient DNA replication fork stability and the activation of growth genes, coordinating DNA replication and gene expression in highly proliferating cells.Support or Funding InformationThis work is supported by NIH Grant 5R01GM111911.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.