XRCC6P5 and pulmonary arterial hypertension: Several DDR pathways are elevated in PASMC from PAH patients including the DNA-damage repair factor poly(ADP-ribose) polymerase-1 (PARP-1)3,7, and the transcription factor FOXM1 that can promote the expression of the DNA repair protein NBS1 (Nijmegen breakage syndrome 1)30.