Tissue and species distribution of mRNA encoding two ADP-ribosylation factors, 20-kDa guanine nucleotide binding proteins

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Abstract
Cholera toxin catalyzed ADP-ribosylation of Gs.alpha., the stimulatory guanine nucleotide binding protein of the adenylyl cyclase system, is enhanced by .apprx.20-kDa guanine nucleotide binding proteins, termed ADP-ribosylation factors or ARFs. ARF is an allosteric activator of the A1 catalytic protein of the toxin. Bovine ARF cDNA clones, ARF-1 isolated from adrenal (Sewell and Kahn, 1988) and ARF-2B from retina (Price et al., 1988), exhibit nucleotide and deduced amino acid sequences athat are 80% and 96% identical, respectively, in the coding region. To determine tissue and species distribution of ARF-like mRNAs, bovine ARF-2B and human ARF-1 cDNAs and 30- or 48-base oligonucleotide probes that distinguish between ARF-1 and ARF-2B cDNAs in coding and 3''-untranslated regions were used for Northern analysis of poly(A+)RNA from different tissues and species. On the basis of hybridization with specific oligonucleotide probes, all bovine tissues contained mRNAs of 1.7 and 2.1 kb that were related to ARF-1 and ARF-2B, respectively. Northern analysis of brain poly(A+)RNA from different species with ARF-2B and ARF-1 cDNAs at low stringency demonstrated several bands varying in size from 0.9 to 3.7 kb. A 1.7-kb band consistently hybridized with an ARF-1 30-base coding-region probe for the 3''-untranslated region. Similar ARF-2B oligonucleotide probes did not hybridize with rat, mouse, rabbit, or human brain mRNA. Cleavage of ARF-2B cDNA with PvuII generated two fragments, one containing coding and the other 3''-noncoding region. Only the coding-region cDNA hybridized with brain poly(A+) RNA from species other than bovine, consistent with other other evidence that the ARF-2B coding region is more highly conserved than the 3''-noncoding region. On the basis of these data and the differences in Nucleotide sequences of ARF-1 and ARF-2B cDNAs, there appear to be at least two highly homologous ARF genes, expressed in a variety of species and tissues.

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