Role of ERCC1 in removal of long non-homologous tails during targeted homologous recombination

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FONTE

Oxford University Press

RESUMO

The XpF/Ercc1 structure-specific endonuclease performs the 5′ incision in nucleotide excision repair and is the apparent mammalian counterpart of the Rad1/Rad10 endonuclease from Saccharomyces cerevisiae. In yeast, Rad1/Rad10 endonuclease also functions in mitotic recombination. To determine whether XpF/Ercc1 endonuclease has a similar role in mitotic recombination, we targeted the APRT locus in Chinese hamster ovary ERCC1+ and ERCC1– cell lines with insertion vectors having long or short terminal non-homologies flanking each side of a double-strand break. No substantial differences were evident in overall recombination frequencies, in contrast to results from targeting experiments in yeast. However, profound differences were observed in types of APRT+ recombinants recovered from ERCC1– cells using targeting vectors with long terminal non-homologies—almost complete ablation of gap repair and single-reciprocal exchange events, and generation of a new class of aberrant insertion/deletion recombinants absent in ERCC1+ cells. These results represent the first demonstration of a requirement for ERCC1 in targeted homologous recombination in mammalian cells, specifically in removal of long non-homologous tails from invading homologous strands.

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