|
Mutants of SGS1, the yeast homolog of the human Bloom
helicase gene, and mismatch repair (MMR) genes are flawed in the
suppression of mitotic recombination between similar but non-identical
sequences, called homeologous sequences, leading to genome instability.
Mutations in the Bloom helicase have been suggested to cause several
types of cancer, including leukemia as well as breast and skin carcinomas
in humans (1). Loss of the inhibition of improper recombination
is indicated by an increase in the ratio of homeologous recombination
to homologous recombination relative to that of wild type. Both
MMR mutants and SGS1 mutants cause an increase in this ratio, and
the double mutant phenotype suggests that Sgs1 acts through the
MMR system to suppress homeologous recombination. It is known that
Sgs1 interacts with MMR proteins (2). In this study, the SGS1 gene
was mutagenized using the pCORE mutagenesis protocol (3), disrupting
the proposed MMR interaction domain of Sgs1 (4). A recombination
assay and subsequent fluctuation analysis was used to determine
the homeologous and homologous recombination rates in the sgs1 point
mutant relative to those of wild type in order to assess the importance
of the interaction of Sgs1 with the MMR system.
|
