Tyrosine phosphorylation of the TATA element modulatory factor by the FER nuclear tyrosine kinases

The FER locus in the mouse encodes two tyrosine kinases, p94(fer) and p51(ferT). While p94(fer) accumulates in the cytoplasm and nucleus of most mammalian cells the expression of p51(ferT) is restricted to the nucleus of meiotic primary spermatocytes. The cellular function of the FER kinases is not understood, nor has a substrate for these enzymes been characterized, To identify putative substrates of p94(fer) and p51(ferT), the two enzymes were used as 'baits' in the yeast two-hybrid screening system. cDNAs encoding the mouse TATA element modulatory factor (TMF) were repeatedly isolated in this assay. TMF was previously shown to bind the TATA element in RNA polymerase II promoters and impaired their functioning in a cell free transcription system. Both p94(fer) and p51(ferT) phosphorylated the TMF protein in in vitro and in vivo kinase assays. Sequential deletions showed that the carboxy-terminal region of TMF was essential for phosphorylation. In situ hybridization analysis revealed the preferential accumulation of TMF transcripts in meiotic spermatogenic and oogenic cells. p94(fer) and p51(ferT) may thus modulate the suppressive activity of TMF during cellular growth and in defined differentiation processes. (C) 1998 Federation of European Biochemical Societies.