Abstract
Ccr4d is a new member of the Ccr4 (carbon catabolite repression 4) family of proteins that are implicated in the regulation of mRNA stability and translation through mRNA deadenylation. However, Ccr4d is not believed to be involved in mRNA deadenylation. Thus, its biological function and mechanistic activity remain to be determined. Here, we report that Ccr4d is broadly expressed in various normal tissues, and the expression of Ccr4d is markedly down-regulated during cell cycle progression. We showed that Ccr4d inhibits cell proliferation and induces cell cycle arrest at G(1) phase. Our experiments further revealed that Ccr4d regulates the expression of p21 in a p53-independent manner. Mechanistic studies indicated that Ccr4d strongly bound to the 3'-UTR of p21 mRNA, leading to the stabilization of p21 mRNA. Interestingly, we found that the expression of Ccr4d is down-regulated in various tumor tissues. Collectively, our data indicate that Ccr4d functions as an anti-proliferating protein through the induction of cell cycle arrest via a p21-dependent and p53-independent pathway and suggest that Ccr4d might have an important role in carcinogenesis.
Highlights
The carbon catabolite repression 4 (Ccr4) family is implicated in RNA processing and modification
We showed that ectopic expression of the endonuclease/exonuclease/phosphatase family protein Ccr4d resulted in inhibition of colony formation and that knockdown of this protein promoted cell growth in MCF-7 breast cancer cells
We demonstrated that ectopic expression of Ccr4d induced G1 arrest, whereas Ccr4d knockdown promoted cell cycle progression in both MCF-7 breast cancer cells and H1299 lung cancer cells
Summary
The carbon catabolite repression 4 (Ccr4) family is implicated in RNA processing and modification. Results: Ccr4d inhibits cell proliferation and induces G1 arrest by binding to p21 mRNA 3Ј-UTR and stabilizing p21 mRNA. Ccr4d is a new member of the Ccr (carbon catabolite repression 4) family of proteins that are implicated in the regulation of mRNA stability and translation through mRNA deadenylation. Our data indicate that Ccr4d functions as an anti-proliferating protein through the induction of cell cycle arrest via a p21-dependent and p53-independent pathway and suggest that Ccr4d might have an important role in carcinogenesis. Ccr4d Induces Cell Cycle Arrest poly(A) tail, is a rate-limiting step in mRNA turnover (18 –20), which involves several deadenylases, including components of the Ccr4-Not complex. We found that Ccr4d is down-regulated in a broad spectrum of tumor samples
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