(L) In early responsive window (1-2 hours after exposure to γ-radiation), while elevation of wild-type KLF4 enhances the expression levels of p21, disruption of KLF4 PARylation diminishes KLF4-mediated p21 accumulation. Upon DNA damage, no matter PARylation or not, elevation of both wild-type or KLF4-PARylation-deficient mutant leads to BRCA1 accumulation suggesting the KLF4-mediated regulation of BRCA1 is independent of PARP1 in MDA-MB-231 cells. 