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

We have analysed the YJR043c gene of Saccharomyces cerevisiae, previously i dentified by systematic sequencing. The deletion mutant (yjr043c Delta) sho ws 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 nuc leus at or beyond the bud neck and a short spindle. This phenotype was even more striking at low temperature, the mutant cells becoming dumbbell shape d. All these phenotypes suggest a role for YJR043C in cell cycle progressio n in G2/M phase. In two-hybrid assays, the YJR043c gene product specificall y 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 los s rate elevated in yjr043c Delta. Analysis of the sequence upstream of the YJR043c ORF revealed the presence of an MluI motif (ACGCGT), a sequence ass ociated with many genes involved in DNA replication in budding yeast. The c ell cycle phenotype of the yjr043c Delta mutant, the evidence for genetic i nteraction with Poll, the presence of an MluI motif upstream and the elevat ed rate of CEN plasmid loss in mutants all support a function for YJR043C i n DNA replication.