Oligomerization of poly(A)-specific ribonuclease(PARN) triggered by the R3H domain

【作者】 何光军； 闫永彬；

【机构】 State Key Laboratory of Biomembrane and Membrane Biotechnology, School of Life Sciences, Tsinghua University；

【摘要】 Poly(A)-specific ribonuclease(PARN),a deadenylase with the unique properties of extremelyhigh catalytic efficiency and cap-dependent processivity,participates in diversephysiological processes by regulating the processing,translation efficiency and decay ofmRNA through deadenylation.PARN is a multi-domain protein containing three RNAbindingdomains(the nuclease,R3H and RRM domains)and a C-terminal domain.Thestructural basis of its high processivity remains unclear.In this research,we found that the purified dimeric PARN could self-associate into tetramerand high-order oligomers by native-PAGE and cross-linking analysis.The oligomerizationof PARN was independent on the binding of substrate and cap.Cross-linking of theproteins in cells revealed that PARN could exist as both homodimer and high-order oligomersin the living cells.Mutational and spectroscopic analysis indicated that PARN oligomerizationwas triggered by R3H domain,which led to the solvent-exposed Trp219fluorophore became buried in a solvent-inaccessible microenvironment.The truncatedmutant with all of the three well-structured RNA-binding domains had the lowest dissociationconstant,while the existence of the C-terminal domain or the removal of the RRMdomain accelerated the dissociation rate of the tetrameric PARN.Enzymatic analysis indicatedthat the tetramerization did not affect the catalytic behavior of the full-length PARNand truncated enzymes with the RRM domain,which might be caused by the highpropensity of the dimeric proteins to self-associate into oligomers.The tet ramerizationsignificantly enhanced the catalytic activity and processivity of the truncated form with theremoval of the RRM and C-terminal domains.The results herein suggested that oligomerizationmight be one of the regulating methods for PARN to achieve a highly regulateddeadenylase activity.We propose that oligomerization may facilitate PARN to concentratearound the target mRNAs in the crowding intracellular conditions.更多还原

【Abstract】 Poly(A)-specific ribonuclease(PARN),a deadenylase with the unique properties of extremelyhigh catalytic efficiency and cap-dependent processivity,participates in diversephysiological processes by regulating the processing,translation efficiency and decay ofmRNA through deadenylation.PARN is a multi-domain protein containing three RNAbindingdomains(the nuclease,R3H and RRM domains)and a C-terminal domain.Thestructural basis of its high processivity remains unclear.In this research,we found that the purified dimeric PARN could self-associate into tetramerand high-order oligomers by native-PAGE and cross-linking analysis.The oligomerizationof PARN was independent on the binding of substrate and cap.Cross-linking of theproteins in cells revealed that PARN could exist as both homodimer and high-order oligomersin the living cells.Mutational and spectroscopic analysis indicated that PARN oligomerizationwas triggered by R3H domain,which led to the solvent-exposed Trp219fluorophore became buried in a solvent-inaccessible microenvironment.The truncatedmutant with all of the three well-structured RNA-binding domains had the lowest dissociationconstant,while the existence of the C-terminal domain or the removal of the RRMdomain accelerated the dissociation rate of the tetrameric PARN.Enzymatic analysis indicatedthat the tetramerization did not affect the catalytic behavior of the full-length PARNand truncated enzymes with the RRM domain,which might be caused by the highpropensity of the dimeric proteins to self-associate into oligomers.The tet ramerizationsignificantly enhanced the catalytic activity and processivity of the truncated form with theremoval of the RRM and C-terminal domains.The results herein suggested that oligomerizationmight be one of the regulating methods for PARN to achieve a highly regulateddeadenylase activity.We propose that oligomerization may facilitate PARN to concentratearound the target mRNAs in the crowding intracellular conditions.更多还原