Isolation and functional analysis of human HMBOX1, a homeobox containing protein with transcriptional repressor activity

We have identified and isolated a novel human gene, <i>HMBOX1</i> (homeobox containing 1) from a pancreatic cDNA library. Human <i>HMBOX1</i> is widely expressed in 18 tissues, and it is highly expressed in pancreas. According to the genome database, <i>HMBOX1</i> is located at the boundary of 8p12.3 and 8p21.1. HMBOX1 proteins are highly conserved in human, mouse, rat, chicken and <i>Xenopus laevis</i>. A phylogenetic tree shows that HMBOX1 may represent a distinct group in HNF (Hepatocyte Nuclear Factor) transcriptional factors. Functional HMBOX1::EGFP (enhanced green fluorescent protein) fusion protein revealed that HMBOX1 accumulated more in cytoplasm than in nucleus. Co-transfection of HEK-293T cells with pM-HMBOX1 plasmid and reporter plasmid pGAL4₅tkLUC indicates that HMBOX1 is a transcription repressor. In situ hybridization on paraffin sections of mouse tissues demonstrated that <i>Hmbox1</i> is widely expressed in pancreas and the expression of this gene can also be detected in pallium, hippocampus and hypothalamus.