FIG. 4.

(A) Relative mRNA levels of the T and B isoforms of fyn in various cell types. mRNA from different cell types was amplified by semiquantitative RT-PCR by using fyn-specific primers bordering exon 7 (which differs in length by three codons between the T and B isoforms). This PCR product was then subjected to a runoff reaction with a fluorescent primer so that the runoff product encompasses the exon 7 region. The length in nucleotides of this runoff product is expected to be 240 nucleotides with a fynT template and 249 nucleotides with a fynB template. This runoff product was then electrophoresed in an automated sequencer, along with size standards. The band pattern for each sample was converted into a profile as shown. The fluorescence and length in nucleotides of the various bands was determined with the Immunoscope software. The percentage of the fynT isoform is indicated in italics in each panel. (B) Relative mRNA levels of the T and B isoforms of fyn in Jurkat clones stably expressing Tax, Rex, and Env. mRNA from different Jurkat clones expressing neomycin resistance alone or together with viral proteins (Tax, Rex, and Env) were amplified by semiquantitative RT-PCR by using fyn-specific primers as described for panel A. The percentage of the fynT isoform is indicated in italics in each panel. (C) Quantification of fynT and fynB mRNAs during a study of the kinetics of induction of Tax by CdCl₂ in JPXM and JPX9 cells. JPXM and JPX9 were cultured in medium alone (NS) or in medium containing 30 μM CdCl₂ for 12, 24, or 36 h. mRNA was amplified by semiquantitative RT-PCR by using fyn-specific primers as described for panel A. The percentage of the fynT isoform is indicated in italics in each panel.