酵母プラスミド2μm DNAの構造と複製

概要

論文の詳細を見る
The yeast Saccharomyces cerevisiae contains 50-100 copies of an autonomously replicating DNA molecule named 2μm DNA. The 2μm DNA is a circular molecule of 6, 300 base-pairs long and contains two invert repeats of 600 base-pairs which are separated from each other by unique segments of 2, 300 and 2, 800 base-pairs. The extensive genetic studies revealed that the replication of 2μm DNA quite resembles that of the yeast chromo- some: each of the 2μm DNA molecule replicates once in each cell cycle, and all of the known gene products involved in the chromosomal replication are also required for the 2μm DNA replication. The 2μm DNA therefore provides an excellent model system for studying the mechanism of eucaryotic chromosome replication.<BR>The in vitro system for the 2μm DNA replication recently developed has elucidated the following characteristics. 1) The replication mostly starts from the specific site which is identical with the in vivo replication origin. 2) The mode of replication is bidirectional and discontinuous. 3) The in vitro 2μm DNA synthesis is temperature sensitive in the extracts prepared from a cell division cycle mutant, cdc 8.<BR>These results indicate that the reactions in the in vitro system reflect the in vivo replication and that proteins participating in the replication of 2μm DNA as well as the yeast chromosome can be characterized by using this in vitro system.