Are MCM genes involved in replication and silencing at HMR in yeast Saccharomyces cerevisiae?
L. Hovland and D. Rivier . Dept. of Cell and Structural Biology, Univ. of Illinois at Urbana-Champaign, 506 Morrill Hall, 505 S. Goodwin Ave, Urbana, IL 61801 In eukaryotic cells, it is essential that every base pair on the chromosome be replicated once and only once per cell cycle. In order to understand initiation of chromosomal replication, I am studying the HMR-E chromosomal origin. Replication may also be required for the repression of transcription of certain genes. Yeast have three nearly identical mating type loci; MAT, HML and HMR. Genes located at MAT are transcribed but genes located at HML and HMR are not transcribed. This position effect, known as silencing, is achieved through flanking DNA sequences (silencers) and a number of proteins. The HMR-E and HMR-I silencers are both origins of replication raising the possibility that replication may be involved in silencing. Furthermore, at least one protein, ORC, is important both for initiation of replication and repression of
