The Saccharomyces cerevisiae protein YJR043C (Pol32) interacts with the catalytic subunit of DNA, polymerase α and is required for cell cycle progression in G2/M

We have analysed the YJR043c gene of Saccharomyces cerevisiae, previously identified by systematic sequencing. The deletion mutant (yjr043c Delta) shows slow growth at low temperature (15 degrees C), while at 30 degrees C and 37 degrees C the growth rate of mutant cells is only moderately affected. At permissive and nonpermissive temperatures, mutant cells were larger and showed a high proportion of large-budded cells with a single duplicated nucleus at or beyond the bud neck and a short spindle. This phenotype was even more striking at low temperature, the mutant cells becoming dumbbell shaped. All these phenotypes suggest a role for YJR043C in cell cycle progression in G2/M phase. In two-hybrid assays, the YJR043c gene product specifically interacted with Poll, the catalytic subunit of DNA polymerase alpha. The pol1-1/yjr043c Delta double mutant showed a more severe growth defect than the pol1-1 single mutant at permissive temperature. Centromeric plasmid loss rate elevated in yjr043c Delta. Analysis of the sequence upstream of the YJR043c ORF revealed the presence of an MluI motif (ACGCGT), a sequence associated with many genes involved in DNA replication in budding yeast. The cell cycle phenotype of the yjr043c Delta mutant, the evidence for genetic interaction with Poll, the presence of an MluI motif upstream and the elevated rate of CEN plasmid loss in mutants all support a function for YJR043C in DNA replication.