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Translation inhibition during cell cycle arrest and apoptosis: Mcl-1 is a novel target for RNA binding protein CUGBP2.
- Source :
- American Journal of Physiology: Gastrointestinal & Liver Physiology; Apr2008, Vol. 294, pG1025-G1032, 8p, 8 Black and White Photographs, 11 Graphs
- Publication Year :
- 2008
-
Abstract
- CUGBP2, a translation inhibitor, induces colon cancer cells to undergo apoptosis. Mcl-1, an antiapoptotic Bcl-2 family protein, interferes with mitochondrial activation to inhibit apoptosis. Here, we have determined the effect of CUGBP2 on Mcl-1 expression. We developed a HCUG<subscript>2</subscript> cell line by stably expressing CUGBP2 in the HCT-116 colon cancer cells. HCUG<subscript>2</subscript> cells demonstrate decreased levels of proliferation and increased apoptosis, compared with HCT-116 cells. Flow cytometry analysis demonstrated higher levels of cells in the G<subscript>2</subscript>-M phase. Western blot analyses demonstrated that there was decreased Bcl-2 and Mcl-1 protein but increased expression of Bax, cyclin B1, and Cdc2. Immunocytochemistry also demonstrated increased levels of cyclin B1 and Cdc2 in the nucleus of HCUG<subscript>2</subscript> cells. However, there was colocalization of phosphorylated histone H3 with transferase- mediated dUTP nick-end labeling (TUNEL). Furthermore, immunostaining for α-tubulin demonstrated that there was disorganization of microtubules. These data suggest that CUGBP2 expression in HCUG<subscript>2</subscript> cells induces the cells to undergo apoptosis during the G<subscript>2</subscript>-M phase of the cell cycle. We next determined the mechanism of CUGBP2- mediated reduction in Mcl-1 expression. Mcl-1 protein, but not Mcl-1 mRNA, was lower in HCUG<subscript>2</subscript> cells, suggesting translation inhibition. CUGBP2 binds to Mcl-1 3′-untranslated region (3′-UTR) both in vitro and in HCUG<subscript>2</subscript> cells. Furthermore, CUGBP2 increased the stability of both endogenous Mcl-1 and luciferase mRNA containing the Mcl-1 3′-UTR. However, luciferase protein expression from the luciferase-Mcl-1 3′-UTR mRNA was suppressed. Taken together, these data demonstrate that CUGBP2 inhibits Mcl-1 expression by inhibiting Mcl-1 mRNA translation, resulting in driving the cells to apoptosis during the G<subscript>2</subscript> phase of the cell cycle. [ABSTRACT FROM AUTHOR]
- Subjects :
- CELL cycle
APOPTOSIS
RNA
CARRIER proteins
COLON cancer
Subjects
Details
- Language :
- English
- ISSN :
- 01931857
- Volume :
- 294
- Database :
- Complementary Index
- Journal :
- American Journal of Physiology: Gastrointestinal & Liver Physiology
- Publication Type :
- Academic Journal
- Accession number :
- 31956250
- Full Text :
- https://doi.org/10.1152/ajpgi.00602.2007