Mouse homolog of the yeast origin recognition complex subunit ORC1 and chromosomal localization of the cognate mouse gene Orc1

ORC1 encodes a subunit of the eukaryotic origin recognition complex in yeas t, which has been shown to play a crucial role in chromosomal DNA replicati on and transcriptional silencing. We have identified a mouse protein closel y related to Saccharomyces cerevisiae ORC1 as well as to the human, Xenopus and Drosophila homologs. MmORC1 has putative cyclin-dependent phosphorylat ion sites and a nucleotide triphosphate-binding motif. We have mapped the g ene locus of the murine Orc1 gene to chromosome 4, band D. Conservation of structures among members of the ORC1-related proteins suggests that these p roteins play a key role in the intiation of DNA replication in all eukaryot es.