Cloning and analysis of coding cDNA sequence of human leukocyte Csk tyrosine kinase under normal conditions and in choroidal melanoma

The main function of Csk tyrosine kinases is phosphorylation of the C-terminal part of Src tyrosine kinases as a mechanism of their downregulation. A decrease in the expression of csk gene results in the enhancement of Src tyrosine kinase activity. In this study, cDNA containing the full coding sequence of the human leukocyte Csk tyrosine kinase gene has been cloned. The protein encoded by a 1624-bp cDNA fragment has 99% homology to human Csk tyrosine kinase. A comparative sequence analysis of full-length cDNAs for Csk tyrosine kinase of normal lymphocytes and lymphocytes of patients with choroidal melanoma revealed a nucleotide substitution in exon 10 of the gene, which appears to be of diagnostic significance. It has been shown that the risk of choroidal melanoma correlated with the frequency of this allele.