Characterization of SpPol4, a unique X-family DNA polymerase in Schizosaccharomyces pombe

• Published in: Nucleic acids research Vol. 33; no. 15; pp. 4762 - 4774
• Main Authors: González-Barrera, Sergio, Sánchez, Arancha, Ruiz, José F., Juárez, Raquel, Picher, Angel J., Terrados, Gloria, Andrade, Paula, Blanco, Luis
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.01.2005; Oxford Publishing Limited (England)
• Subjects: Amino Acid Sequence; Deoxyribonucleotides - metabolism; DNA Nucleotidylexotransferase - metabolism; DNA Primers; DNA Repair; DNA-Directed DNA Polymerase - classification; DNA-Directed DNA Polymerase - genetics; DNA-Directed DNA Polymerase - metabolism; Exodeoxyribonucleases - metabolism; Genomic Imprinting; Molecular Sequence Data; Phosphates - chemistry; Phosphorus-Oxygen Lyases - metabolism; Purines - metabolism; Ribonucleotides - metabolism; Schizosaccharomyces - enzymology; Schizosaccharomyces - genetics; Schizosaccharomyces pombe Proteins - classification; Schizosaccharomyces pombe Proteins - genetics; Schizosaccharomyces pombe Proteins - metabolism; Templates, Genetic
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gki780

As predicted by the amino acid sequence, the purified protein coded by Schizosaccharomyces pombe SPAC2F7.06c is a DNA polymerase (SpPol4) whose biochemical properties resemble those of other X family (PolX) members. Thus, this new PolX is template-dependent, polymerizes in a distributive manner, lacks a detectable 3′→5′ proofreading activity and its preferred substrates are small gaps with a 5′-phosphate group. Similarly to Polμ, SpPol4 can incorporate a ribonucleotide (rNTP) into a primer DNA. However, it is not responsible for the 1–2 rNTPs proposed to be present at the mating-type locus and those necessary for mating-type switching. Unlike Polμ, SpPol4 lacks terminal deoxynucleotidyltransferase activity and realigns the primer terminus to alternative template bases only under certain sequence contexts and, therefore, it is less error-prone than Polμ. Nonetheless, the biochemical properties of this gap-filling DNA polymerase are suitable for a possible role of SpPol4 in non-homologous end-joining. Unexpectedly based on sequence analysis, SpPol4 has deoxyribose phosphate lyase activity like Polβ and Polλ, and unlike Polμ, suggesting also a role of this enzyme in base excision repair. Therefore, SpPol4 is a unique enzyme whose enzymatic properties are hybrid of those described for mammalian Polβ, Polλ and Polμ.