CLONING AND MOLECULAR CHARACTERIZATION OF COMPLEMENTARY DEOXYRIBONUCLEIC-ACID CORRESPONDING TO A NOVEL FORM OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE MESSENGER-RIBONUCLEIC-ACID IN THE RAT TESTIS

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropep tide that greatly stimulates adenylyl cyclase activity in cultured ant erior pituitary cells, was isolated from ovine hypothalamus in 1989. I nvestigation of the distribution of PACAP messenger RNA (mRNA) in rat tissues by Northern blot analysis revealed an anomalous signal in the testis. In this study we have isolated and characterized this unusual mRNA, which is approximately 800 bases long (similar to 1.5 kilobases shorter than that reported in the rat hypothalamus). Cloning and seque ncing of the complementary DNA corresponding to this message revealed that the sequences are identical except for 126 bases at the 5'-end of the 5'-untranslated region of the smaller transcript. This region has no homology to either the published hypothalamic sequence or any othe r known sequence. Northern blot analysis of total RNA from various spe cies showed that a smaller form of PACAP mRNA is also present in human , murine, and bovine testis, although in these species the message is slightly smaller. In addition, Northern blot analysis of these tissues using a probe directed to the 126-base 5'-region, revealed conservati on of this sequence between species. Although the structure of the rat PACAP gene is unknown, preliminary investigations into the origins of the two mRNA species by PCR of genomic DNA suggests that they are tra nscribed rate genes and not the product of alternate splicing.