Transcript-Specific Decapping and Regulated Stability by the Human Dcp2 Decapping Protein

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Abstract
MRNA decapping is a critical step in the control of mRNA stability and gene expression and is carried out by the Dcp2 decapping enzyme. Dcp2 is an RNA binding protein that must bind RNA in order to recognize the cap for hydrolysis. We demonstrate that human Dcp2 (hDcp2) preferentially binds to a subset of mRNAs and identify sequences at the 5' terminus of the mRNA encoding Rrp41, a core subunit component of the RNA exosome, as a specific hDcp2 substrate. A 60-nucleotide element at the 5' end of Rrp41 mRNA was identified and shown to confer more efficient decapping on a heterologous RNA both in vitro and upon transfection into cells. Moreover, reduction of hDcp2 protein levels in cells resulted in a selective stabilization of the Rrp41 mRNA, confirming it as a downstream target of hDcp2 regulation. These findings demonstrate that hDcp2 can specifically bind to and regulate the stability of a subset of mRNAs, and its intriguing regulation of the 3'-to-5' exonuclease exosome subunit suggests a potential interplay between 5'-end mRNA decapping and 3'-end mRNA decay.