Aphidicolin-resistant and -sensitive base excision repair in wild-type and DNA polymerase beta-defective mouse cells |
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Authors: | Parlanti Eleonora Pascucci Barbara Terrados Gloria Blanco Luis Dogliotti Eugenia |
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Institution: | Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Roma, Italy. |
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Abstract: | Several DNA polymerases (Pols) can add complementary bases at the gap created during the base excision repair (BER). To characterize the BER resynthesis step, the repair of a single abasic site by wild-type and Pol beta-defective mouse cell extracts was analysed in the presence of aphidicolin, a specific inhibitor of replicative Pols. We show that there is a competition between distributive and processive Pols for the nucleotide addition at the primer terminus. In wild-type cell extracts, the initial nucleotide insertion involves mainly Pol beta but the elongation step is carried out by a replicative Pol. Conversely, in Pol beta-null cell extracts the synthesis step is carried out by a replicative Pol without any switching to an auxiliary polymerase. We present evidence that short-patch repair synthesis occurs even in the absence of both Pol beta and replicative Pols. Exogeneously added purified human Pol lambda was unable to stimulate this back-up synthesis. |
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