Plays a key role in the repair of DNA damage, functioning as part of both the non-homologous end-joining (NHEJ) and base excision repair (BER) pathways (PubMed:10446192, PubMed:10446193, PubMed:15385968, PubMed:20852255, PubMed:28453785). Through its two catalytic activities, PNK ensures that DNA termini are compatible with extension and ligation by either removing 3'-phosphates from, or by phosphorylating 5'-hydroxyl groups on, the ribose sugar of the DNA backbone (PubMed:10446192, PubMed:10446193). {ECO:0000269|PubMed:10446192, ECO:0000269|PubMed:10446193, ECO:0000269|PubMed:15385968, ECO:0000269|PubMed:20852255, ECO:0000269|PubMed:28453785}. This is the function of Ensembl gene identifier ENSG00000039650 (PNKP, polynucleotide kinase 3'-phosphatase).