POLN, a nuclear PolA family DNA polymerase homologous to the DNA cross-link sensitivity protein Mus308.
The Drosophila Mus308 gene is unusual in encoding both a family A DNA polymerase domain and a DNA/RNA helicase domain. A mus308 mutation was shown to result in increased sensitivity to DNA cross-linking agents, leading to the hypothesis that Mus308 functions in the repair of DNA interstrand cross-links. Recently a mammalian ortholog of Mus308, POLQ, has been identified. We report here the identification, cloning, and characterization of POLN and its gene product, a new mammalian DNA polymerase also related to Mus308. The human cDNA encodes a protein of 900 amino acid residues. The region starting from residue 419 shares 33% identity (48% similarity) with the equivalent region of Escherichia coli DNA polymerase I. POLN is expressed in human cell lines with numerous alternatively spliced transcripts, and a full-length human coding region that comprises 24 exons within 160 kilobases of genomic DNA. Expression analysis by northern blotting and in situ hybridization showed highest expression of full-length POLN in human and mouse testis. POLN localized to the nucleus when expressed as a enhanced green fluorescent protein (GFP)-tagged protein in human fibroblasts. GFP-tagged recombinant POLN had DNA polymerase activity on activated calf thymus DNA and on a singly primed template.
Marini
Federica
F
University of Pittsburgh Cancer Institute, Hillman Cancer Center, Research Pavilion, Pittsburgh, Pennsylvania 15213, USA.
Kim
Nayun
N
Schuffert
Anthony
A
Wood
Richard D
RD
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D004247:DNA / Q000378:metabolism*; D004256:DNA Polymerase I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D045643:DNA Repair Enzymes; D004259:DNA-Directed DNA Polymerase; D029721:Drosophila Proteins; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000201:enzymology; D000097462:DNA Polymerase theta
D004247:DNA; D004256:DNA Polymerase I; D017931:DNA Primers; D045643:DNA Repair Enzymes; D004259:DNA-Directed DNA Polymerase; D029721:Drosophila Proteins; C101782:DNApol-theta protein, Drosophila; D000097462:DNA Polymerase theta