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The Pol β variant containing exon α is deficient in DNA polymerase but has full dRP lyase activity
DNA polymerase (Pol) β is a key enzyme in base excision repair (BER), an important repair system for maintaining genomic integrity. We previously reported the presence of a Pol β transcript containing exon α (105-nucleotide) in normal and colon cancer cell lines. The transcript carried an insertion...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Nature Publishing Group UK
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6616571/ https://www.ncbi.nlm.nih.gov/pubmed/31289286 http://dx.doi.org/10.1038/s41598-019-45846-0 |
Sumario: | DNA polymerase (Pol) β is a key enzyme in base excision repair (BER), an important repair system for maintaining genomic integrity. We previously reported the presence of a Pol β transcript containing exon α (105-nucleotide) in normal and colon cancer cell lines. The transcript carried an insertion between exons VI and VII and was predicted to encode a ~42 kDa variant of the wild-type 39 kDa enzyme. However, little is known about the biochemical properties of the exon α-containing Pol β (exon α Pol β) variant. Here, we first obtained evidence indicating expression of the 42 kDa exon α Pol β variant in mouse embryonic fibroblasts. The exon α Pol β variant was then overexpressed in E. coli, purified, and characterized for its biochemical properties. Kinetic studies of exon α Pol β revealed that it is deficient in DNA binding to gapped DNA, has strongly reduced polymerase activity and higher Km for dNTP during gap-filling. On the other hand, the 5′-dRP lyase activity of the exon α Pol β variant is similar to that of wild-type Pol β. These results indicate the exon α Pol β variant is base excision repair deficient, but does conduct 5′-trimming of a dRP group at the gap margin. Understanding the biological implications of this Pol β variant warrants further investigation. |
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