Regulation of cellular proliferation by the BTG2 protein
Mechanism by which BTG2 stimulates the shortening of mRNA poly(A) tails. In the absence of BTG2, the CAF1 deadenylase has a limited activity (top illustration). BTG2, that has the capacity to bind both the CAF1 deadenylase and the Poly(A)-Binding Protein (PABP), allows to recruit and to position efficiently CAF1 on its substrate: the mRNA poly (A) tail. Consequently, BTG2 stimulates the poly(A) tail degradation by CAF1 (bottom illustration).
Nat Commun Feb. 25, 2016
Feb. 25, 2016
Researchers of the IGBMC determined the mechanism of action of the protein BTG2 in the degradation of messenger RNAs. In spite of its important properties, its mechanism of action at the molecular level was still unclear. The newly discovered process allows BTG2 to control cellular proliferation. The results were published in Nature Communications on February 25, 2016.
Expression of the genetic material ends up in the production of proteins from messenger RNAs (mRNAs). The nature and quantity of mRNAs present in a cell are essential for the correct cellular functions. One of the goals of the team of Bertrand SERAPHIN is to understand how the process of RNA turnover contributes to the regulation of gene expression and to the elimination of defective transcripts.
Several pathways participating to the degradation of eukaryotic RNA have been identified. In humans, as in other eukaryotes, the first step of the mRNA degradation pathway is the shortening of their poly(A) tail, a process also known as deadenylation. This step is generally catalyzed by the CAF1 deadenylase enzyme. BTG2 belongs to the BTG/Tob family of proteins. These proteins are characterized by a common mode of interaction with the CAF1 deadenylase. BTG2 was implicated in many biological processes. Interestingly, the level of BTG2 is frequently decreased in cancer cells and correlates with tumor grade and survival of patients.
The biological effect of the protein BTG2
The researchers observed previously that expression of BTG2 in cells stimulated the deadenylation of mRNAs by an unknown mechanism. The results now published by the team of Bertrand SERAPHIN reveal an unexpected interaction of the protein BTG2 with a poly(A)-binding domain of the PABP protein. The latter wraps the mRNA poly(A) tails in cells. These observations allowed for the first time to reconstitute the stimulation of CAF1 deadenylase activity in vitro. This process requires the participation of the BTG2 and PABP proteins only.
The scientists showed that through its interaction with PABP and its capacity to stimulate deadenylation, BTG2 limits the cellular proliferation. Further work will reveal whether a reduced level of BTG2 favors the fast and uncontrolled growth of cancer cells. Treatments controlling the level of BTG2 could then be considered.