CLONING AND CHARACTERIZATION OF MST, A NOVEL (PUTATIVE) SERINE THREONINE KINASE WITH SH3 DOMAIN

Protein kinases play a key role in cell growth regulation. We have iso lated a cDNA fragment of the MST gene from the MKN28 gastric cancer ce ll line cDNA pool by degenerate polymerase chain reaction. MST-cDNAs w ere cloned from the human brain cDNA library. Nucleotide sequence anal ysis indicated that the MST gene encodes a novel putative non-receptor type of serine/threonine kinase with Src homology 3 (SH3) domain, two leucine zipper domains and proline rich domain. The deduced amino aci d sequence corresponding to a part of kinase domain and leucine zipper domains of MST (amino acid codons 244-461) is almost identical to the published partial amino acid sequence of MLK2. MST is the first non-r eceptor type of serine/threonine kinase containing SH3 domain, leucine zipper domain and proline rich domain other than PTK1/Sprk. The MST g ene was moderately expressed in brain, skeletal muscle and testis as a 3.8 kb mRNA, and the MST gene has been mapped to human chromosome 19q 13.1-q13.2.