ARS sequences in homologous and heterologous ADE2 loci are capable of promoting autonomous replication of plasmids in Schwanniomyces occidentalis

We have analyzed ARS elements linked to homologous and heterologous ADE2 lo ci functioning in Schwanniomyces occidentalis. We have identified a region of the ADE2 locus of S. occidentalis which promotes autonomous replication of plasmids in S. occidentalis cells. This region is within 385 bp precedin g the ATG codon of the S. occidentalis ADE2 gene. It contains sequences sim ilar to ARS core consensus sequences, ARS boxes, and a potential transcript ion activator binding site characterized in Saccharomyces cerevisiae. The A DE2 gene of S. cerevisiae was found to complement the ade2 mutation in S. o ccidentalis cells and the 5' UTR region of this gene is capable of supporti ng autonomous replication of plasmids in S. occidentalis. Furthermore, we c onfirmed that the origin of replication of the 2 mu m plasmid and the ARS1 sequence of S. cerevisiae are also functional in S. occidentalis cells. Pla smids carrying either ARS, the SwARSA element of S. occidentalis, the ARS l inked to the ADE2 gene of S. cerevisiae, and the ARSI sequence or the 2 mu m ori, were found to be maintained in S. occidentalis cells as episomal mon omers or oligomers. However, their stability was low as aleady reported for the ARS in S. occidentalis.