Stimulation of hTAFII68 (NTD)-mediated transactivation by v-Src

AbstractThe three genes hTAFII68, EWS, and TLS (called the TET family) encode related RNA binding proteins containing an RNA recognition motif and three glycine-, arginine-, and proline-rich regions in the C-terminus and a degenerated repeat containing the consensus sequence Ser-Tyr-Gly-Gln-Ser in the N-terminus. In many human cancers, the N-terminal portion of hTAFII68, EWS, or TLS is fused to the DNA binding domain of one of several transcription factors including Fli-1, ERG, ETV1, E1AF, WT1, ATF-1, CHOP, or TEC. We have recognized the presence of several potential tyrosine phosphorylation sites within the amino-terminal domain of hTAFII68 and have investigated the potential effects of cytoplasmic signaling on hTAFII68 function. Herein, we find that hTAFII68 is phosphorylated on tyrosine residue(s) by ectopic expression of v-Src protein tyrosine kinase in vitro and in vivo. The hTAFII68 protein can associated with the SH3 domains of several cell signaling proteins, including v-Src protein tyrosine kinase. We also document that full-length v-Src can stimulate hTAFII68-mediated transcriptional activation, whereas deletion mutants of v-Src are unable to exert this effect. In addition, cellular Src activity appears important for hTAFII68 function since hTAFII68-mediated transactivation is reduced in a dose-dependent fashion by ectopic overexpression of a dominant-negative mutant of Src. Taken together, our results suggest that the biological activities of hTAFII68 are linked to the cytoplasmic Src signal transduction pathway