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Updated: Jul 13, 2026
Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using χCRAC
Published on: May 9, 2020
PAB1 self-association precludes its binding to poly(A), thereby accelerating CCR4 deadenylation in vivo
Gang Yao1, Yueh-Chin Chiang, Chongxu Zhang
1Department of Biochemistry and Molecular Biology, Rudman Hall, University of New Hampshire, Durham, NH 03824, USA.
Abstract:
The mRNA deadenylation process, catalyzed by the CCR4 deadenylase, is known to be the major factor controlling mRNA decay rates in Saccharomyces cerevisiae. We have identified the proline-rich region and RRM1 domains of poly(A) binding protein (PAB1) as necessary for CCR4 deadenylation. Deletion of either of these regions but not other regions of PAB1 significantly reduced PAB1-PAB1 protein interactions, suggesting that PAB1 oligomerization is a required step for deadenylation. Moreover, defects in these two regions inhibited the formation of a novel, circular monomeric PAB1 species that forms in the absence of poly(A). Removal of the PAB1 RRM3 domain, which promoted PAB1 oligomerization and circularization, correspondingly accelerated CCR4 deadenylation. Circular PAB1 was unable to bind poly(A), and PAB1 multimers were severely deficient or unable to bind poly(A), implicating the PAB1 RNA binding surface as critical in making contacts that allow PAB1 self-association. These results support the model that the control of CCR4 deadenylation in vivo occurs in part through the removal of PAB1 from the poly(A) tail following its self-association into multimers and/or a circular species. Known alterations in the P domains of different PAB proteins and factors and conditions that affect PAB1 self-association would, therefore, be expected to be critical to controlling mRNA turnover in the cell.
Insights
Poly(A)-binding protein (PAB1) self-association, particularly its proline-rich and RRM1 regions, is crucial for CCR4 deadenylation, controlling mRNA decay rates in yeast. This process involves PAB1 multimerization and circularization, impacting its poly(A) binding ability.
Area of Science:
- Molecular Biology
- Yeast Genetics
- RNA Metabolism
Background:
- mRNA deadenylation is a key regulator of mRNA decay rates in Saccharomyces cerevisiae.
- The CCR4 deadenylase complex is the primary enzyme responsible for this process.
Purpose of the Study:
- To investigate the role of poly(A)-binding protein (PAB1) domains in CCR4-mediated deadenylation.
- To elucidate the mechanism by which PAB1 influences mRNA decay.
Main Methods:
- Site-directed mutagenesis of PAB1 to delete specific domains (proline-rich region, RRM1, RRM3).
- Analysis of PAB1-PAB1 protein interactions and PAB1 oligomerization.
- Assessment of CCR4 deadenylation rates in yeast strains with mutated PAB1.
Main Results:
- The proline-rich region and RRM1 domain of PAB1 are essential for CCR4 deadenylation.
- Deletion of these regions impairs PAB1 self-association (oligomerization) and the formation of a circular PAB1 species.
- Removal of the RRM3 domain, which promotes PAB1 oligomerization, accelerates CCR4 deadenylation.
- Both circular and multimeric PAB1 forms exhibit reduced or absent poly(A) binding, suggesting the RNA-binding surface is critical for self-association.
Conclusions:
- PAB1 self-association into multimers or circular species is a prerequisite for CCR4-mediated deadenylation.
- The control of mRNA turnover is linked to PAB1's ability to self-associate and its interaction with the poly(A) tail.
- Alterations in PAB1 self-association mechanisms can significantly impact cellular mRNA decay rates.
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