MOLECULAR-CLONING OF RODENT P72(SYK) - EVIDENCE OF ALTERNATIVE MESSENGER-RNA SPLICING

Northern blot analysis of polyadenylated RNA prepared from RBL-2H3 cel ls revealed the presence of three distinct mRNAs encoding p72(Syk), a protein-tyrosine kinase previously shown to be associated with the hig h affinity IgE receptor present on the surface of these cells (Hutchcr oft, J. E., Geahlen, R. L., Deanin, G. G., and Oliver, J. M. (1992) Pr oc. Natl. Acad. Sci. U.S.A. 89, 9107-9111), Here we report the full-le ngth nucleotide sequence of two of these messages, as well as the comp lete predicted amino acid sequence of the rodent p72(Syk) protein-tyro sine kinase. In addition, we report evidence indicating alternative sp licing of p72(Syk) mRNAs within RBL-2H3 cells. This splicing event res ults in the expression of two distinct protein isoforms that differ wi th respect to the presence of a 23-amino acid insert located within th e region of the protein that separates the two SH2 domains from the ca talytic domain. Both mRNAs arising from this splicing event appear to encode functional protein-tyrosine kinases, as expression of the corre sponding cDNAs in COS cells results in the production of proteins of t he expected sizes that possess intrinsic tyrosine specific kinase acti vity.