Completion of replication map of Saccharomyces cerevisiae chromosome III

In Saccharomyces cerevisiae chromosomal DNA replication initiates at interv als of similar to 40 kb and depends upon the activity of autonomously repli cating sequence (ARS) elements. The identification of ARS elements and anal ysis of their function as chromosomal replication origins requires the use of functional assays because they are not sufficiently similar to identify by DNA sequence analysis. To complete the systematic identification of ARS elements on S. cerevisiae chromosome III, overlapping clones covering 140 k b of the right arm were tested for their ability to promote extrachromosoma l maintenance of plasmids. Examination of chromosomal replication intermedi ates of each of the seven ARS elements identified revealed that their effic iencies of use as chromosomal replication origins varied widely, with four ARS elements active in less than or equal to 10% of cells in the population and two ARS elements active in greater than or equal to 90% of the populat ion. Together with our previous analysis of a 200-kb region of chromosome I II, these data provide the first complete analysis of ARS elements and DNA replication origins on an entire eukaryotic chromosome.