Pat1 activates late steps in mRNA decay by multiple mechanisms
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Published on: July 10, 2019
Joseph H Lobel1,2, Ryan W Tibble1,2, John D Gross3
1Chemistry and Chemical Biology Graduate Program, University of California, San Francisco, CA 94158.
Abstract:
Pat1 is a hub for mRNA metabolism, acting in pre-mRNA splicing, translation repression, and mRNA decay. A critical step in all 5'-3' mRNA decay pathways is removal of the 5' cap structure, which precedes and permits digestion of the RNA body by conserved exonucleases. During bulk 5'-3' decay, the Pat1/Lsm1-7 complex engages mRNA at the 3' end and promotes hydrolysis of the cap structure by Dcp1/Dcp2 at the 5' end through an unknown mechanism. We reconstitute Pat1 with 5' and 3' decay factors and show how it activates multiple steps in late mRNA decay. First, we find that Pat1 stabilizes binding of the Lsm1-7 complex to RNA using two conserved short-linear interaction motifs. Second, Pat1 directly activates decapping by binding elements in the disordered C-terminal extension of Dcp2, alleviating autoinhibition and promoting substrate binding. Our results uncover the molecular mechanism of how separate domains of Pat1 coordinate the assembly and activation of a decapping messenger ribonucleoprotein (mRNP) that promotes 5'-3' mRNA degradation.
Insights
Pat1 protein stabilizes RNA decay complexes and directly activates decapping, a crucial step in mRNA degradation. This reveals how Pat1 coordinates messenger ribonucleoprotein assembly for 5'-3' RNA decay.
Area of Science:
- Molecular Biology
- RNA Metabolism
- Biochemistry
Background:
- Pat1 protein is central to mRNA metabolism, influencing splicing, translation repression, and decay.
- 5 -3 mRNA decay requires 5 -cap removal before RNA body digestion by exonucleases.
- The Pat1/Lsm1-7 complex interacts with mRNA at the 3 end to promote decapping by Dcp1/Dcp2.
Purpose of the Study:
- To elucidate the molecular mechanism by which Pat1 activates mRNA decay.
- To understand how Pat1 coordinates the assembly and activation of the decapping messenger ribonucleoprotein (mRNP).
Main Methods:
- Reconstitution of Pat1 with 5 and 3 decay factors.
- Analysis of Pat1 interactions with the Lsm1-7 complex and Dcp2.
- Biochemical assays to assess decapping activation.
Main Results:
- Pat1 stabilizes Lsm1-7 complex binding to RNA via two conserved interaction motifs.
- Pat1 directly activates Dcp2-mediated decapping by binding its C-terminal extension, relieving autoinhibition.
- Pat1 facilitates substrate binding to Dcp2.
Conclusions:
- Pat1 acts as a scaffold, coordinating the assembly of the decapping mRNP.
- Pat1's distinct domains facilitate Lsm1-7 binding and Dcp2 activation, driving 5 -3 mRNA decay.
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