PTK6 (protein tyrosine kinase 6, BRK or FLJ42088), with 451-amino acid protein (about 52kDa), encods a cytoplasmic nonreceptor protein kinase which may function as an intracellular signal transducer in epithelial tissues. Its presence in the nucleus appears to be linked to suppression of tumor progression. The encoded protein has been shown to undergo autophosphory-lation. Very high level in colon and high levels in small intestine and prostate, and low levels in some fetal tissues. And Expressed at low level in some breast tumors, but not in normal breast. Also found in melanocytes, but not expressed in heart, brain, placenta, lung, liver, skeletal muscle, kidney and pancreas. Overexpression of this gene in mammary epithelial cells leads to sensitization of the cells to epidermal growth factor and results in a partially transformed phenotype.