Replication of the 2-micrometer DNA plasmid of yeast.

The 2-micrometer DNA plasmid of yeast provides an useful probe for the analysis of the factors involved in the initiation of chromosomal DNA replication in the cell division cycle. Cell-free extracts prepared from growing yeast cells stimulate DNA replication directed by this plasmid. The plasmid replicating activity is subject to control in the yeast cell cycle. The 2-micrometer DNA plasmid can be isolated from logarithmically-growing cells in association with yeast folded chromosomes. The interaction of the plasmid with structures in the cell corresponding to the folded chromosome appears dynamic and cell cycle-dependent. Thus, not only the induction and activity of the proteins involved in replication, but also the intracellular locus of a replicon may be important factors in the control of initiation of DNA replication.