Alternative splicing at exon 2 results in the loss of the catalytic activity of mouse DNA polymerase iota in vitro

• Published in: DNA repair Vol. 50; pp. 77 - 82
• Main Authors: Kazachenko, Konstantin Y., Miropolskaya, Nataliya A., Gening, Leonid V., Tarantul, Vyacheslav Z., Makarova, Alena V.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.02.2017
• Subjects: Alternative Splicing; Amino Acid Sequence; Animals; Catalytic Domain; DNA polymerase activity; DNA polymerase iota; DNA Repair; DNA Replication; DNA-Directed DNA Polymerase - chemistry; DNA-Directed DNA Polymerase - genetics; DNA-Directed DNA Polymerase - isolation & purification; DNA-Directed DNA Polymerase - metabolism; dRP lyase activity; Exons; Mice; Sequence Alignment; Sequence Deletion; DNA polymerase activity; Alternative splicing; dRP lyase activity; DNA polymerase iota
• ISSN: 1568-7864; 1568-7856; 1568-7856
• DOI: 10.1016/j.dnarep.2017.01.001

•The catalytic properties of mouse Pol ι are similar to human Pol ι.•129-derived strains of mice harbor a nonsense codon in exon 2 of the Pol ι gene.•Pol ι mRNA undergoes alternative splicing at exon 2.•Purified Pol ι missing exon 2 region lacks the polymerase and dRP lyase activities. Y-family DNA polymerase iota (Pol ι) possesses both DNA polymerase and dRP lyase activities and was suggested to be involved in DNA translesion synthesis and base excision repair in mammals. The 129 strain of mice and its derivatives have a natural nonsense codon mutation in the second exon of the Pol ι gene resulting in truncation of the Pol ι protein. These mice were widely used as a Pol ι-null model for in vivo studies of the Pol ι function. However whether 129-derived strains of mice are fully deficient in the Pol ι functions was a subject of discussion since Pol ι mRNA undergoes alternative splicing at exon 2. Here we report purification of mouse Pol ι lacking the region encoded by exon 2, which includes several conserved residues involved in catalysis. We show that the deletion abrogates both the DNA polymerase and dRP lyase activities of Pol ι in the presence of either Mg2+ or Mn2+ ions. Thus, 129-derived strains of mice express catalytically inactive alternatively spliced Pol ι variant, whose cellular functions, if any exist, remain to be established.