MOUSE AND HUMAN HOMOLOGS OF THE YEAST ORIGIN OF REPLICATION RECOGNITION COMPLEX SUBUNIT ORC2 AND CHROMOSOMAL LOCALIZATION OF THE COGNATE HUMAN GENE ORC2L

ORC2 is a subunit of the origin recognition complex in yeast and has b een implicated in the initiation of DNA replication and transcriptiona l silencing. We have isolated mouse and human cDNA clones encoding pro teins with 47.9 and 46.3% similarity, respectively, to yeast ORC2. Thi s degree of similarity and the alignment of sequences suggest that the se clones may represent a mammalian ORC2 homologue. The existence of s uch a homologue would, in turn, suggest the existence of a mammalian o rigin recognition complex, similar to that found in yeast. Although No rthern blot analysis of various adult mouse tissues found the highest levels of expression of ORC2-like (ORC2L) RNA in testes, strong signal s did not always correspond to tissues in which high levels of DNA rep lication would be expected. This finding may reflect functional roles of ORC2L distinct from those that it may play in DNA replication. Anal yses of somatic cell hybrid DNA and fluorescence in situ hybridization were employed to map the human ORC2L gene to chromosome 2q33. (C) 199 6 Academic Press, Inc.