RT Journal Article
SR Electronic
T1 Structural Insights into γH2Ax containing Nucleosomes
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2023.04.30.538894
DO 10.1101/2023.04.30.538894
A1 Rashmi Panigrahi
A1 Ross Edwards
A1 Md Touhidul (Apu) Islam
A1 Jun Lu
A1 Ayodeji Kulepa
A1 Tae Hwan Kim
A1 J. N. Mark Glover
YR 2023
UL http://biorxiv.org/content/early/2023/05/01/2023.04.30.538894.abstract
AB MDC1 is a key mediator of DNA-damage signaling. When DNA double-strand breaks (DSB) occur, the histone variant H2AX on the nucleosome is phosphorylated on its C-terminus at residue Ser139 to form the γH2AX nucleosome. This phosphorylated form is specifically recognized by the tandem BRCT repeats of MDC1. The MDC1-bound nucleosome serves as a docking platform to promote the localization of other DNA repair factors. To further characterize the nucleosome-BRCT interaction, we developed a time efficient two-step modified native chemical ligation protocol to prepare phosphorylated nucleosomes. Our binding studies show that BRCT interacts with the nucleosome with a higher affinity than the phosphorylated peptide. Using cryogenic electron microscopy (cryo-EM), we obtained structures of the γH2AX nucleosome revealing the structural basis for nucleosome-nucleosome stacking promoted by interactions of the H4 N-terminal of one nucleosome with its stacked partner. In contrast, we show that binding of the MDC1 BRCT domain disrupts this stacking, suggesting that histone/DNA dynamics are integral to DNA damage signaling.Competing Interest StatementThe authors have declared no competing interest.