Characterization of mammalian orthologues of the Drosophila osa gene: cDNAcloning, expression, chromosomal localization, and direct physical interaction with Brahma chromatin-remodeling complex

The osa gene of Drosophila melanogaster encodes a nuclear protein that is a component of the Brahma chromatin-remodeling complex. Osa is required for embryonic segmentation, development of the notum and wing margin, and photo receptor differentiation. In these tissues, osa mutations have effects oppo site to those caused by wingless (wg) mutations, suggesting that osa functi ons as an antagonist of wg signaling. Here we describe the cloning and char acterization of mammalian orthologues of osa. Three evolutionarily conserve d domains were identified in Osa family members: the N-terminal Bright doma in and C-terminally located Osa homology domains 1 and 2, RNase protection analysis indicates a widespread expression of the Osa1 gene during mouse de velopment, in adult tissues, and in cultured cell lines. The Osa1 gene was localized to mouse chromosome 4, within the region syntenic to chromosomal position 1p35-p36 of its human counterpart. We present evidence that the OS Al product is localized in the nucleus and associates with human Brahma com plex, which suggests evolutionarily conserved function for Osa in gene regu lation between mammals and Drosophila. (C) 2001 Academic Press.