Has minor DNA joining activity. Can act on oligo(PDT)/poly(rA) substrate. ATP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + AMP + diphosphate. Interacts with LIF1 via its BRCT domain. Interacts with POL4 in the DNL4-LIF1 complex. Belongs to the ATP-dependent DNA ligase family. Produces 2 separate ORFs. Produces 2 separate ORFs.