DNA damage-induced phosphorylation of histone H2A at serine 15 is linked to DNA end resection

Abstract

The repair of DNA double-strand breaks (DSBs) occurs in chromatin and several histone post-translational modifications have been implicated in the process. Modifications of histone H2A N-terminal tail has also been linked to DNA damage response, through acetylation or ubiquitination of lysine residues that regulate repair pathway choice. Here, we characterize a new DNA damage-induced phosphorylation on chromatin, at serine 15 of H2A in yeast. We show that this SQ motif functions independently of the classical S129 C-terminal site ({gamma}H2A) and mutant mimicking constitutive phosphorylation increases cell sensitivity to DNA damage. H2AS129ph is induced by Tel1ATM and Mec1ATR, and loss of Lcd1ATRIP or Mec1 signaling decreases {gamma}H2A spreading distal to the DSB. In contrast, H2AS15ph is completely dependent on Lcd1ATRIP, indicating that this modification only happens when end resection is engaged. This is supported by an increase of RPA and a decrease in DNA signal near the DSB in the H2AS-15E phosphomimic mutant, indicating higher resection. This serine is replaced by a lysine in mammals (H2AK15), which undergoes an acetyl-monoubiquityl switch to regulate binding of 53BP1 and resection. This regulation seems functionally conserved with budding yeast H2AS15 and 53BP1-homolog Rad9, using different post-translational modifications between organisms but achieving the same function.