Allele-specific interactions between the yeast RFC1 and RFC5 genes suggest a basis for RFC subunit-subunit interactions.

Replication factor C (RFC) is an essential, multi-subunit ATPase that functions in DNA replication, DNA repair, and DNA metabolism-related checkpoints. In order to investigate how the individual RFC subunits contribute to these functions in vivo, we undertook a genetic analysis of RFC genes from budding yeast. We isolated and characterized mutations in the RFC5 gene that could suppress the cold-sensitive phenotype of rfc1-1 mutants. Analysis of the RFC5 suppressors revealed that they could not suppress the elongated telomere phenotype, the sensitivity to DNA damaging agents, or the mutator phenotype of rfc1-1 mutants. Unlike the checkpoint-defective rfc5-1 mutation, the RFC5 suppressor mutations did not interfere with the methylmethane sulfonate- or hydroxyurea-induced phosphorylation of Rad53p. The Rfc5p suppressor substitutions mapped to amino acid positions in the conserved RFC box motifs IV-VII. Comparisons of the structures of related RFC box-containing proteins suggest that these RFC motifs may function to coordinate interactions between neighboring subunits of multi-subunit ATPases.