Identification of hepatocyte growth factor activator inhibitor type 2 (HAI-2)-related small peptide (H2RSP): Its nuclear localization and generation of chimeric mRNA transcribed from both HAI-2 and H2RSP genes

A novel small gene, designated hepatocyte growth factor activator inhibitor type 2 (HAI-2)-related small peptide (H2RSP) was cloned and characterized in the process of the search for splicing variant forms of HAI-2 by X-rapid amplification of cDNA ends (RACE). The gene consisted of 4 exons spanning approximately 1 kb and was located in 11 kb downstream of HAI-2 gene (19q.1 3.11). The novel transcript identified by X-RACE was thought to be chimeric ally transcribed from both HAI-2 (exons 1-7) and H2RSP (exons 2-4) genes. W ildtype H2RSP mRNA (0.5 kb) was detected abundantly in various tissues incl uding the gastrointestinal tract, whereas chimeric mRNA (1.5 kb) was found mainly in the kidney, prostate, and placenta by Northern blot analysis. The predicted amino acid sequence of H2RSP contained two unique domains, namel y the serine-rich region (exon 3) and the lysine-rich region (exon 4). Tran sfection of deleted series of H2RSP cDNAs fused to enhanced green fluoresce nt protein (EGFP) into HeLa cells revealed that H2RSP has nuclear localizat ion signal in the lysine-rich region. Immunohistochemical study using anti- H2RSP polyclonal antibody indeed revealed the nuclear localization of this peptide in vivo. These results suggest that H2RSP and H2RSP/HAI-2 chimeric peptides might function as a transcriptional regulatory peptide at the nucl eus. (C) 2001 Academic Press.