Functional characterization of the gene encoding RLIM, the corepressor of LIM homeodomain factors.

RLIM is a RING H2 zinc finger protein that acts as a negative coregulator for LIM homeodomain transcription factors. We have isolated genomic lambda clones that cover the entire mouse RLIM-encoding Rnf12 gene. The Rnf12 gene encompasses 20 kb and consists of at least five exons and four introns. Several transcriptional start sites within a 24-bp region were mapped around 300 nt upstream of the translational start site. Rnf12-specific mRNA can be detected in many tissues as revealed by Northern blot analysis. Transient cotransfections reveal that the proximal Rnf12 promoter can be activated in vitro by ubiquitously and more restrictively expressed transcription factors, some of which are known mediators of signal transduction pathways, e.g., mammalian Krüppel-like transcription factors, Sox and ets-related proteins, and RBP-J. We isolated a cDNA encoding human RLIM, which is highly conserved with mouse and chick RLIM. By fluorescence in situ hybridization and interspecific backcross analysis, we have localized the Rnf12 gene to the central regions of mouse and human chromosome X. Copyright 2000 Academic Press.