Abstract
The BRCA1 COOH terminus (BRCT) motif is present in many nuclear proteins that contribute to cell cycle regulation or DNA repair. Polymerase chain reaction-based screening with degenerate primers targeted to the BRCT motif resulted in the isolation of a human cDNA for a previously unidentified DNA polymerase (designated DNA polymerase beta2) that is closely related to DNA polymerase beta (Pol beta). The predicted Pol beta2 protein contains a BRCT motif in its NH(2)-terminal region; its COOH-terminal region exhibits 33% sequence identity to a corresponding region of human Pol beta. The Pol beta2 gene is expressed in a tissue-specific manner, with transcripts being most abundant in testis. A fusion construct comprising Pol beta2 and green fluorescent protein exhibited a predominantly nuclear localization in transfected HeLa cells. Recombinant human Pol beta2 from insect cells exhibited substantial DNA polymerase activity, but it did not possess terminal deoxyribonucleotidyl transferase activity. A truncated Pol beta2 mutant lacking the BRCT motif retained substantial DNA polymerase activity, whereas a mutant Pol beta2 with two alanine point mutations within the DNA polymerase active site did not. These results indicate that Pol beta2 is a Pol beta-related DNA polymerase with a BRCT motif that is dispensable for its polymerase activity.
Highlights
The human BRCA1 gene, which determines susceptibility to familial breast and ovarian cancer [1], encodes a predicted protein of 1863 amino acids whose NH2-terminal region contains a single RING finger, a domain present in various proteins that exhibit transactivation activity at the promoter of
The BRCA1 COOH terminus (BRCT) motif is present in many nuclear proteins that contribute to cell cycle regulation or DNA repair
A truncated polymerase  (Pol )2 mutant lacking the BRCT motif retained substantial DNA polymerase activity, whereas a mutant polymerase 2 (Pol 2) with two alanine point mutations within the DNA polymerase active site did not. These results indicate that Pol 2 is a Pol -related DNA polymerase with a BRCT motif that is dispensable for its polymerase activity
Summary
The human BRCA1 gene, which determines susceptibility to familial breast and ovarian cancer [1], encodes a predicted protein of 1863 amino acids whose NH2-terminal region contains a single RING finger, a domain present in various proteins that exhibit transactivation activity at the promoter of. The BRCA1 COOH terminus (BRCT) motif is present in many nuclear proteins that contribute to cell cycle regulation or DNA repair. The predicted Pol 2 protein contains a BRCT motif in its NH2-terminal region; its COOH-terminal region exhibits 33% sequence identity to a corresponding region of human Pol .
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