What comes first in the DDR out of PARP activation and ATM/ATR mediated phosphorylation of H2AX? Is PARP required for the appearance of yH2AX or vice versa (i.e. ATM/ATR/yH2AX activate PARP)?
Poly(ADP-ribosyl)ation is the first PTM happening at the DNA-damage foci. It precedes the phosphorylation events and it is required to recruit the DDR apparatus.