Cloning, chromosomal location, and expression analysis of murine Smarce1-related, a new member of the high-mobility 365 group gene family.

Proteins containing high-mobility group (HMG) domains are segregated into two major groups. Members of one group are identified by the presence of more than one HMG domain that binds to DNA without sequence specificity, and they are usually ubiquitously expressed. In contrast, members of the other group possess a single HMG domain with high affinity to specific DNA sequences. Generally, members of the second group resemble classic tissue-specific transcriptional regulators. In contrast, Smarce1/BAF-57 is a ubiquitously expressed, novel protein with a single HMG domain that displays nonspecific DNA-binding characteristics. Additionally, as a core subunit of the mammalian SWI/SNF-like transcriptional activator complex, Smarce1/BAF-57 is also the first member of the HMG protein family that was reported to contain a kinesin-like coiled-coil (KLCC) domain. Here we report the cloning, as well as the chromosomal and phylogenetic analysis, of a novel mammalian protein that is structurally related to Smarce1, termed Smarce1-related (Smarce1r). The unique arrangement of an HMG with a KLCC domain shared with Smarce1/BAF-57 suggests a similar, albeit still unknown, function in chromatin assembly as part of a mammalian SWI/SNF-like complex. The linkage of a single nonspecific DNA-binding HMG domain with a KLCC domain makes both proteins the founding members of a third group of HMG proteins.