Melanomas resist conventional chemotherapeutics in part through intrinsic disrespect of apoptotic checkpoint activation. In this study, using an unbiased genome-wide RNAi screen we identified RhoJ and its effector Pak1, as key modulators of melanoma cell sensitivity to DNA damage. We find that RhoJ activates Pak1 in response to drug-induced DNA damage, which then uncouples ATR from its downstream effectors, ultimately resulting in a blunted DNA damage response (DDR). In addition, ATR suppression leads to the decreased phosphorylation of ATF2, and consequent increased expression of the melanocyte survival gene Sox10 resulting in a higher DDR threshold required to engage melanoma cell death. In the setting of normal melanocyte behavior, this regulatory relationship may facilitate appropriate epidermal melanization in response to UV-induced DNA damage.
Read more: RhoJ and Pak Kinases Regulate Melanoma Chemoresistance by Suppressing Pathways that Sense DNA Damage