Cloning and characterization of the gene encoding the mouse homologue of CpG binding protein

Human CpG binding protein (CGBP) is a ubiquitously-expressed transcriptional activator that binds specifically to unmethylated CpG motifs. Several protein domains have been identified within CGBP including two plant homeodomains (PHD), acidic and basic regions, a coiled-coil domain, as well as a CXXC DNA-binding domain. The global function of CGBP remains unclear, although failure to express CGBP results in embryonic lethality in mice. This study reports the identification and characterization of the murine CGBP gene locus. A 2509 bp murine CGBP cDNA was cloned and nucleotide sequence determined. Comparison of the mouse and human CGBP sequences revealed 86% identity at the nucleotide level and 96% identity at the amino acid level. Examination of the deduced translation product revealed that the PHD, CXXC, coiled-coil, and basic domains are identical between mouse and human, while the acidic region exhibits approximately 90% identity with its human counterpart. A single murine CGBP transcript of approximately 2.6 kb was detected in a wide variety of adult tissues as well as embryonic stem cells. Analysis of the mouse gene locus revealed a relatively small gene spanning approximately 5 kb and comprised of 15 exons. Examination of the human CGBP gene showed a similar size and structure with identical intronic splice sites. In contrast to the human CGBP gene, which is located 800 bp upstream of the MBD1 gene, analysis of the murine CGBP gene locus failed to detect the murine MBD1 gene within several kilobases of the CGBP coding region.