Replication and recombination functions associated with the yeast plasmid, 2μ circle

By examining both the transformation efficiency of yeast of various plasmids containing defined regions of the 2μ circle genome and the characteristics of the resultant transformants, we have identified several regions of the 2μ circle genome which are involved in 2μ circle replication or recombination. First, by identifying those DNA fragments from the molecule which promote high frequency transformation of yeast, we have localized the origin of replication to a sequence partially within the large unique region, which, as determined by subsequent deletion analysis, extends from the middle of the inverted repeat region into the contiguous unique region. Second, by examining the relative efficiency of replication in yeast of hybrid plasmids containing either the entire 2μ circle genome or a fragment of 2μ circle encompassing the origin of replication, we have determined that efficient use of the 2μ circle origin requires some function or functions encoded in the molecule at a site away from the origin. Third, by examining the ability of a mutant 2μ circle molecule to undergo intramolecular recombination in yeast, we have identified a 2μ circle gene which codes for a product required for this process