Single-strand-binding factor(s) which interact with ARS1 of Saccharomyces cerevisiae

Since plasmids containing autonomously replicating sequence(s) (ARS) can transform Saccharomyces cerevisiae cells at high frequency, ARS are considered to be the replication origins of chromosomes. To study the mechanism of initiation of eukaryotic chromosomal replication, we examined protein factors which interact with the ARS1 region located near the centromere of chromosome IV in S. cerevisiae. Using the gel-shift assay, we found protein factors which bound to a single-stranded, 97-bp fragment of the ARS1 region containing the core consensus. Competition experiments with various oligodeoxyribonucleotides (oligos) suggest that a site recognized by the factor(s) was within the element containing the core consensus and adjacent close matches to the core consensus of the minus strand. Indeed, when the oligo containing the minus strand of this element was used as a probe, two oligo-protein complexes were detected. Mutations in the core consensus reduced these binding activities. When the plus-strand oligo of the same region was used as a probe, a retarded band was also detected, but with less specific binding. Considering the fact that the core consensus and close matches to the core consensus are important for ARS function, these results imply that the protein factors detected in this experiment may participate in DNA replication.