Cloning and functional characterization of the HRASLS2 gene

The HRAS-like suppressor 2 ( HRASLS2 ) gene belongs to the H-REV107 gene family involved in the regulation of cell growth and differentiation. HRASLS2 is expressed at high levels in normal tissues of the small intestine, kidney, and trachea. We cloned HRASLS2 cDNA from human SW480 colon cancer cells. Most wild-type, and some N- and C-terminal truncated HRASLS2 (HRASLS2ΔNΔC) were expressed as a granular pattern located at perinuclear region in HtTA cervical cancer cells, while truncation at the C-terminus only (HRASLS2ΔC) resulted in a diffuse pattern. Wild-type HRASLS2 significantly suppressed colony formation of HeLa and HCT116 cells. HRASLS2ΔNΔC significantly inhibited colony formation of HCT116 cells, but HRASLS2ΔC did not affect cell growth. HRASLS2 suppressed the RAS-GTP levels and total RAS protein by 44% and 25%, respectively in HtTA cells; however, the suppression was not observed in truncated HRASLS2 variants. In conclusion, the HRASLS2 protein suppressed growth and RAS activities of cancer cells, and the C-terminal hydrophobic domain appeared to be indispensable for both activities.