SEQUENCE-INDEPENDENT DETECTION OF GENE FAMILY HOMOLOGS - IDENTIFICATION OF A TRANSCRIPT ENCODING A MOLLUSCAN SERINE-PROTEASE HOMOLOGOUS TO THE PANCREATIC-ENZYMES OF VERTEBRATES

Autoradiography of P-32-labeled cDNA, fractionated at high resolution by electrophoresis through thin (0.8-1.5 mm) vertical alkaline agarose gels, provides a sequence-independent screening procedure for gene family homologs, A screen of tissues of a marine mollusc revealed a prominent intestine-specific cDNA encoding a pancreatic serine protease homolog, which was not detectable as a discrete poly(A)(+) RNA species on formaldehyde agarose gels, Discrete cDNA products are authentic, non-truncated transcripts of tissue-specific mRNA. A band-sharpening effect is imparted to cDNA products due to (a) substitution of a uniform length 5'-oligo(dT) terminus for heterogeneous 3'-poly(A) termini rind (b) the inherent superior resolution of alkaline-denatured DNA,