title: Self-association of poly(A)-specific ribonuclease (PARN) triggered by the R3H domain.
abstract: Poly(A)-specific ribonuclease (PARN) is a deadenylase with three RNA-binding domains (the nuclease, R3H and RRM domains) and a C-terminal domain. PARN participates in diverse physiological processes by regulating mRNA fates through deadenylation. PARN mainly exists as a dimer in dilute solutions. In this research, we found that PARN could self-associate into tetramer and high-order oligomers both in vitro and in living cells. Mutational and spectroscopic analysis indicated that PARN oligomerization was triggered by the R3H domain, which led to the solvent-exposed Trp219 fluorophore to become buried in a solvent-inaccessible microenvironment. The RRM and C-terminal domains also played a role in modulating the dissociation rate of the tetrameric PARN. Enzymatic analysis indicated that tetramerization did not affect the catalytic behavior of the full-length PARN and truncated enzymes containing the RRM domain, which might be caused by the high propensity of the dimeric proteins to self-associate into oligomers. Tetramerization significantly enhanced the catalytic activity and processivity of the truncated form with the removal of the RRM and C-terminal domains. The results herein suggested that self-association might be one of the regulation methods for PARN to achieve a highly regulated deadenylase activity. We propose that self-association may facilitate PARN to concentrate around the target mRNAs by restricted diffusion.
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Guang-Jun
authors.initials: GJ
authors.lastname: He
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University, Beijing 100084, China. Electronic address: ybyan@tsinghua.edu.cn.
authors.forename: Yong-Bin
authors.initials: YB
authors.lastname: Yan
keywords: Deadenylation; Oligomerization; Poly(A)-specific ribonuclease (PARN); Processivity; Restricted diffusion; mRNA decay