CHL12, a gene essential for the fidelity of chromosome transmission in the yeast Saccharomyces cerevisiae.

We have analyzed the CHL12 gene, earlier identified in a screen for yeast mutants with increased rates of mitotic loss of chromosome III and circular centromeric plasmids. A genomic clone of CHL12 was isolated and used to map its physical position on the right arm of chromosome XIII near the ADH3 locus. Nucleotide sequence analysis of CHL12 revealed a 2.2-kb open reading frame with a 84-kD predicted protein sequence. Analysis of the sequence upstream of the CHL12 open reading frame revealed the presence of two imperfect copies of MluI motif, ACGCGT, a sequence associated with many DNA metabolism genes in yeast. Analysis of the amino acid sequence revealed that the protein contains a NTP-binding domain and shares a low degree of homology with subunits of replication factor C (RF-C). A strain containing a null allele of CHL12 was viable under standard growth conditions, and as well as original mutants exhibited an increase in the level of spontaneous mitotic recombination, slow growth and cold-sensitive phenotypes. Most of cells carrying the null chl12 mutation arrested as large budded cells with the nucleus in the neck at nonpermissive temperature that typical for cell division cycle (cdc) mutants that arrest in the cell cycle at a point either immediately preceding M phase or during S phase. Cell cycle arrest of the chl12 mutant requires the RAD9 gene. We conclude that the CHL12 gene product has critical role in DNA metabolism.