32 DNA Replication in Yeast

Abstract

The details of chromosome replication are better understood in the budding yeast, Saccharomyces cerevisiae , than in any other eukaryotic organism. cis -Acting replicator sequences required for chromosomal replication origin function were identified on the basis of their ability to promote the extrachromosomal maintenance of plasmids. These autonomously replicating sequence (ARS) elements have been dissected using the plasmid assay. The ease with which chromosomal sequences can be replaced by homologous recombination in this yeast has facilitated analysis of the effects of ARS mutations on chromosomal origin activity, which can be assayed by two-dimensional (2D) gel analysis. Both the isolation and analysis of mutants defective in DNA replication and the use of reverse genetics to identify and mutate genes encoding proteins thought to participate in DNA replication have yielded insights into proteins required for the initiation and elongation steps of DNA replication. The fission yeast, Schizosaccharomyces pombe , offers many of the same advantages for the study of chromosomal DNA replication as S. cerevisiae . A similar plasmid assay has been used to identify ARS elements that appear to be associated with chromosomal replication origins. The sequences required for ARS activity in the plasmid assay have not been dissected thoroughly, but preliminary indications suggest that S. pombe ARS elements, like S. pombe centromeres, are larger than those of S. cerevisiae. In addition, the genes encoding a number of S. pombe replication proteins have been isolated and characterized. Despite the enormous progress in characterizing the replicators and proteins required for yeast chromosomal DNA replication, there is...