LigD_Pol_like: Polymerase (Pol) domain of bacterial LigD proteins similar to Pseudomonas aeruginosa (Pae) LigD. The LigD Pol domain belongs to the archaeal/eukaryal primase (AEP) superfamily. In prokaryotes, LigD along with Ku is required for non-homologous end joining (NHEJ)-mediated repair of DNA double-strand breaks (DSB). NHEJ-mediated DNA DSB repair is error-prone. PaeLigD is monomeric, containing an N-terminal phosphoesterase module, a central polymerase (Pol) domain, and a C-terminal ATP-dependent ligase domain. Mycobacterium tuberculosis (Mt)LigD, also found in this group, is monomeric and contains the same modules but these are arranged differently: an N-terminal Pol domain, a central phosphoesterase module, and a C-terminal ligase domain. It has been suggested that LigD Pol contributes to NHEJ-mediated DNA DSB repair in vivo, by filling in short 5'-overhangs with ribonucleotides; the filled in termini would then be sealed by the associated LigD ligase domain, resulting in short stretches of RNA incorporated into the genomic DNA. The PaeLigD Pol domain in vitro, in a manganese-dependent fashion, catalyzes templated extensions of 5'-overhang duplex DNA, and nontemplated single-nucleotide additions to blunt-end duplex DNA; it preferentially adds single ribonucleotides at blunt DNA ends. PaeLigD Pol adds a correctly paired rNTP to the DNA primer termini more rapidly than it does a correctly paired dNTP; it has higher infidelity as an RNA polymerase than it does as a DNA polymerase, which is in keeping with the mutagenic property of NHEJ-mediated DNA DSB repair. The MtLigD Pol domain similarly is stimulated by manganese, is error-prone, and prefers adding rNTPs to dNTPs in vitro. The MtLigD Pol domain has been shown to prefer DNA gapped substrates containing a 5'-phosphate group at the gap.