A Protein Is Unusual Tumor Suppressor

Cancer researchers have shown that the tumor-suppressing protein REG-gamma activates the proteasome-mediated destruction of the protein product of the powerful oncogene steroid receptor coactivator-3 (SRC-3).

Investigators at Baylor College of Medicine (Houston, TX, USA) used RNA interference (RNAi) technology to "knockdown” the activity of REG-gamma. Their results published in the January 27, 2006, issue of Cell showed that reduction of REG-gamma activity allowed the overexpression of SRC-3 with subsequent stimulation of tumor cell growth. In vitro proteasome proteolysis assays using purified REG-gamma, SRC-3, and the 20S proteasome demonstrated that REG-gamma promoted the degradation of SRC-3 in an ubiquitin- and ATP-independent manner.

"It is another intervention point where one can now attack tumors. It is especially important for endocrine tumors such as those of the breast, prostate, ovary, and pituitary gland,” said senior author Dr. Bert O'Malley, professor of molecular and cellular biology at Baylor College of Medicine. "This is an important pathway for SRC3 degradation that has never been described. This molecule does not require ubiquitin or an energy source, it is a really strange and different molecule for that reason.”



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