cDNA, genomic cloning, and gene expression analysis of mouse PSP94 (Prostate secretory protein of 94 amino acids)

The potential use of prostate secretory protein of 94 amino acids (PSP94) a s a diagnostic biomarker or a therapeutic agent for prostate cancer has bee n reported. In order to establish an animal model to further elucidate on i ts biological role, we cloned the mouse PSP94 cDNA (similar to 500 bp) by r everse transcriptase-polymerase chain reaction (RT-PCR) and disclosed its g enomic structure. The whole mouse PSP94 gene (similar to 23 kb) was amplifi ed by long and accurate-PCR and also cloned by screening of a mouse embryo stem-cell genomic library. Computational and statistical analyses have demo nstrated several highly conserved characteristics of PSP94 among different species. Comparison of PSP94 from human, two primates, pig, and rodents rev ealed that the most significant feature is that PSP94 is rich in cysteines (10% of the total sequence) and their positions are highly conserved. The t hree intron-four exon structure of the human PSP94 gene and the consensus s equence (....GT-intron-AG....) for mRNA splicing are also strongly conserve d. A high divergence in cDNA sequence in the protein-coding region and also in the genomic sequence of PSP94 was also observed among these species. Co mparing with alpha-globin, a typical evolutionally conserved gene, with the PSP94 gene, the rate of nonsynonymous changes per site per year (k(N)) is 2 to 6 times higher, indicating that PSP94 gene has been under far fewer ev olutionary constraints than other genes and has a potential role as a speci es barrier in reproductive biology. In order to test this hypothesis, we in vestigated the gene expression of PSP94 and its tissue distribution in vari ous rodent tissues by RT-PCR and in situ hybridization (ISH), Gene expressi on was found only in the prostate, suggesting that PSP94 is probably more t issue specific in the prostate of rodents than in mammals. The ISH analysis also revealed a prostate lobe-specific expression of the PSP94 gene in bot h mice and rats. It was strongly expressed in the lateral prostate, but the findings were negative in the dorsal and ventral lobe, Therefore, it is hy pothesized that one of the primary functions of rodent PSP94, as a major pr ostate secretory protein, is related to reproductive biology.