IDENTIFICATION OF A NOVEL GENE - SSK1 - IN HUMAN ENDOTHELIAL-CELLS EXPOSED TO SHEAR-STRESS

To identify transcriptionally regulated genes potentially involved in the effect of shear stress on endothelial gene expression, we performe d a differential display analysis of mRNAs from human umbilical vein e ndothelial cell (HUVEC) exposed to laminar shear stress (12 dynes/cm(2 )) in comparison to HUVEC maintained in static condition. We identifie d a cDNA fragment overexpressed by laminar shear stress. The full-leng th, SSK1, was 3653 long and encoded for a novel protein of 1050 amino acids. Northern blot demonstrates that SSK1 mRNA is expressed at high levels also in placenta, a weak transcript was present in heart, skele tal muscle, kidney and pancreas. Homology searches of the protein data bases showed that SSK1 is related to numerous serine-threonine kinases . The highest homology was found with a very recently described gene, BUBR1, an analogue of BUB1, which is a kinase involved in the regulati on of cell cycle. The most conserved residues in catalytic domains II, III, VIb, VII, VIII and IX of serine-threonine protein kinases were f ound in the C terminal region of SSK1 which further supports the kinas e nature of the new protein. The putative serine-threonine kinase SSK1 may represent a tool by which mechanical forces regulates phosphoryla tion events within endothelial cells. (C) 1998 Academic Press.