Involved in the base excision repair (BER) pathway, by catalyzing the poly (ADP-ribosyl)ation of a limited number of acceptor proteins involved in chromatin architecture and in DNA metabolism. This modification follows DNA damages and appears as an obligatory step in a detection/signaling pathway leading to the reparation of DNA strand breaks. Mediates serine ADP-ribosylation of target proteins following interaction with HPF1; HPF1 conferring serine specificity.