IDENTIFICATION OF THE 5TH SUBUNIT OF SACCHAROMYCES-CEREVISIAE REPLICATION FACTOR-C

Yeast replication factor C (RF-C) is a multipolypeptide complex requir ed for chromosomal DNA replication, Previously this complex was known to consist of at least four subunits. We here report the identificatio n of a fifth RF-C subunit from Saccharomyces cerevisiae, encoded by th e RFC5 (YBR0810) gene. This subunit exhibits highest homology to the 3 8 kDa subunit (38%) of human RF-C (activator 1). Like the other four R FC genes, the RFCS gene is essential for yeast viability, indicating a n essential function for each subunit. RFCS mRNA is expressed at stead y-state levels throughout the mitotic cell cycle. Upon overexpression in Escherichia coli Rfc5p has an apparent molecular mass of 41 kDa. Ov erproduction of RF-C activity in yeast is dependent on overexpression of the RFCS gene together with overexpression of the RFC1-4 genes, ind icating that the RFCS gene product forms an integral subunit of this r eplication factor.