IDENTIFICATION OF THE YEAST MCM3-RELATED PROTEIN AS A COMPONENT OF XENOPUS DNA-REPLICATION LICENSING FACTOR

Replication licensing factor is thought to be involved in the strict c ontrol of the initiation of DNA replication in eukaryotes. We identifi ed a 100 kDa protein as a candidate for the licensing factor in Xenopu s egg extracts. This protein was required for replication; it bound to sperm DNA before the formation of nuclei and apparently dissociated f rom the nuclear DNA during the progression of replication without bein g transported into the nuclei. An immunologically homologous protein i n HeLa cells behaved similarly to the Xenopus protein during the cell cycle. Cloning and sequencing of the cDNAs encoding the Xenopus and hu man proteins revealed that they are homologs of yeast Mcm3, a putative yeast DNA replication licensing factor.