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The mouse B-raf gene encodes multiple protein isoforms with tissue-specific expression.

J V Barnier·C Papin·A Eychène·O Lecoq·G Calothy
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Abstract

The c-Rmil/B-raf proto-oncogene is a member of the mil/raf family encoding serine/threonine protein kinases shown to be involved in signal transduction from the membrane to the nucleus. We isolated from a mouse brain library B-raf cDNAs containing a previously unidentified 36-base pair alternatively spliced exon located between exons 8 and 9 and, therefore, designated exon 8b. Human and mouse B-raf mRNAs also contain the 120-base pair alternatively spliced exon 10 previously described in the avian c-Rmil gene. Independent splicing of these two exons, located between the conserved region 2 (CR2) and the catalytic domain (CR3) gives rise to mRNAs potentially encoding four distinct proteins. By using specific sera generated against different portions of B-Raf, we identified at least 10 protein isoforms in adult mouse tissues. Some isoforms, in the range of 69-72 kDa, are not recognized by antisera directed against peptides encoded by exons 1 and 2, indicating the existence of B-Raf proteins with two different NH2 extremities. The other isoforms, in the range of 79-99 kDa, contain the amino acids encoded by exons 1 and 2, by either or both of the alternatively spliced exons, and, possibly, by another of the unidentified exon. Analysis of B-raf mRNA expression by reverse transcriptase-polymerase chain reaction and immunocharacterization of B-Raf proteins in different tissues of the adult mouse showed a tissue-specific pattern of B-Raf isoforms expression. Interestingly, isoforms containing amino acids encoded by exon 10 are specifically expressed in neural tissues. Taken together, these results suggest that distinct B-Raf proteins could be involved, in a tissue-specific manner, in signal transduction pathways.

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Alternative SplicingAmino Acid SequenceAnimalsAntibody SpecificityBase SequenceBirdsDNA PrimersDNA, ComplementaryExonsGene ExpressionHumansMaleMiceMolecular Sequence DataProtein Serine-Threonine KinasesProto-Oncogene MasProto-Oncogene ProteinsProto-Oncogene Proteins c-rafProto-OncogenesRNA, MessengerSignal TransductionTissue DistributionJournal ArticleResearch Support, Non-U.S. Gov't

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J V Barnier, C Papin, A Eychène, O Lecoq, G Calothy. 1995-10-06. The mouse B-raf gene encodes multiple protein isoforms with tissue-specific expression.. https://doi.org/10.1074/jbc.270.40.23381

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