Cloning and characterization of human and mouse SNRK sucrose non-fermenting protein (SNF-1)-related kinases

Abstract We previously isolated, from the earliest population of CD34 + hematopoietic progenitors that form in the aorta of the human embryo, a partial DNA complementary to RNA (cDNA) sequence that was later identified as the human homologue of rat sucrose non-fermenting protein (SNF-1) related kinase (r SNRK ), a novel SNF-1-related kinase previously characterized in the rat. In the present study we report the cloning of the complete human SNF-1 related kinase (h SNRK ) cDNA and show that the gene spans 39.8 kb at region 3p21 and contains six exons. Recombinant expression of the h SNRK coding sequence in Escherichia coli led to the production of a functional protein kinase of 85 kDa. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of h SNRK expression in fetal CD34 + hematopoietic progenitors revealed its continuous expression throughout human development with higher levels in highly dividing CD34 + CD38 + cells compared to quiescent CD34 + CD38 − cells. This observation, together with the expression of h SNRK in numerous human leukemic cell lines, may reflect an implication of hSNRK protein in hematopoietic cell proliferation or differentiation. In the mouse, the SNRK cDNA is 4.6-kb-long and encodes a protein of 748 amino acids with a predicted molecular mass of 81,930 Da. The proteins from human, rat and mouse are strongly conserved and are characterized by the presence of a serine/threonine kinase catalytic domain, a bipartite nuclear targeting signal and an ubiquitin-associated domain. In situ hybridization and RT-PCR analysis of the pattern of m SNRK expression in the mouse reveals that it is temporally and spatially regulated during embryogenesis, and widespread expressed in adult tissues.