Increased tyrosine-phosphorylation of 55KDa proteins in beta-actin/Tec transgenic mice

Protein-tyrosine kinases are considered to play important roles in cell proliferation and differentiation. Tec is a cytoplasmic protein-tyrosine kinase expressed in liver and hematopoietic tissues. To better understand Tec function in vivo, we generated transgenic mice expressing tec driven by the cytomegarovirus enhancer and beta-actin promoter. Among six transgenic lines generated, a particular line, named 2-11, expressed tec transgene product more widely and abundantly than the other lines. In the tissues of 2-11, the kinase activity of Tec was enhanced in accordance with the high expression of tec transgene product. Interestingly, tyrosine-phosphorylation of approximately 55KDa proteins in the tissues was induced. These results suggest that cellular proteins of 55KDa might be potential substrates of Tec in vivo.