COMPARISON OF THE 2 MAJOR ARS ELEMENTS OF THE URA4 REPLICATION ORIGINREGION WITH OTHER ARS ELEMENTS IN THE FISSION YEAST, SCHIZOSACCHAROMYCES-POMBE

We have previously reported that the replication origin region located near the ura4 gene on chromosome III of the fission yeast, Schizosacc haromyces pom be, contains three closely spaced origins, each associat ed with an autonomously replicating sequence (ARS) element. Here we re port the nucleotide sequences of two of these ARS elements, ars3002 an d ars3003. The two ARS elements are located on either side of a transc ribed 1.5 kb open reading frame. Like 11 other S. pombe ARS elements w hose sequences have previously been determined in other laboratories, the 2 new ARS elements are unusually A+T-rich. All 13 ARS elements con tain easily unwound stretches of DNA. Each of the ARS elements contain s numerous copies, at a higher than expected frequency, of short stret ches of A+T-rich DNA in which most of the Ts are on one strand and mos t of the As are on the complementary strand. We discuss the potential significance for ARS function of these multiple asymmetric A+T-rich se quences.