IDENTIFICATION OF A PREDOMINANT REPLICATION ORIGIN IN FISSION YEAST

We have identified five autonomously replicating sequences (ARSs) in a 100 kbp region of the Schizosaccharomyces pombe chromosome II. Analys es of replicative intermediates of the chromosome DNA by neutral/neutr al two-dimensional gel electrophoresis demonstrated that at least thre e of these ARS loci operate as chromosomal replication origins, One of the loci, ori2004, was utilized in almost every cell cycle, while the others were used less frequently The frequency of initiation from the respective chromosomal replication origin was found to be roughly pro portional to the efficiency of autonomous replication of the correspon ding ARS plasmid, Replication from ori2004 was initiated within a dist inct region almost the same as that for replication of the ARS plasmid , These results showed that the ori2004 region of similar to 3 kbp con tains all the cis elements essential for initiation of chromosome repl ication.