MOLECULAR-CLONING AND ANALYSIS OF THE HUMAN TEC PROTEIN-TYROSINE KINASE

Mouse Tec is a non-receptor type protein-tyrosine kinase and is highly expressed in many hematopoietic cell lines. To investigate the roles of the Tec kinase in the human hematopoietic system, we isolated cDNAs encoding the human Tec kinase. The human tee cDNAs can encode a pepti de of 631 amino acid residues with a calculated molecular mass of 73 6 24. The predicted human Tec protein is highly homologous to those of t he members of the Tec family including mouse Tec type IV (94% homology ), mouse Tsk/Itk (60%), and human Btk (57%). The homology between huma n Tec and other members of the Tec family can be observed not only in the Src homology 3 (SH3), SH2, and kinase domains, but also in the N-t erminal unique domain. Northern blot analysis demonstrated that the ma jor transcripts of tee could be detected at 2.6 kb and 3.6 kb in a wid e range of human hematopoietic cell lines including myeloid, B-, and T -cell lineages. Interestingly, high expression of the tee gene could b e detected in all of the three patients examined with myelodysplastic syndrome. The human fee gene was mapped by fluorescence in situ hybrid ization (FISH) to chromosome 4p12.