THE ARS309 CHROMOSOMAL REPLICATOR OF SACCHAROMYCES-CEREVISIAE DEPENDSON AN EXCEPTIONAL ARS CONSENSUS SEQUENCE

Autonomously replicating sequence (ARS) elements, which function as th e cis-acting chromosomal replica tors in the yeast Saccharomyces cerev isiae, depend upon an essential copy of the Il-bp ARS consensus sequen ce (ACS) for activity, Analysis of the chromosome III replicator ARS30 9 unexpectedly revealed that its essential ACS differs from the canoni cal ACS at two positions, One of the changes observed in ARS309 inacti vates other ARS elements, This atypical ACS binds the origin recogniti on complex efficiently and is required for chromosomal replication ori gin activity, Comparison of the essential ACS of ARS309 with the essen tial regions of other ARS elements revealed an expanded 17-bp conserve d sequence that efficiently predicts the essential core of ARS element s.