scholarly journals Structural Insights into Negative Cooperativity between Gemin2 and RNA in Sm-class snRNP Assembly

2019 ◽  
Author(s):  
Rundong Zhang
Keyword(s):  
Spinal Muscular Atrophy ◽  
Neurodegenerative Disease ◽  
Muscular Atrophy ◽  
Structural Mechanics ◽  
Atomic Resolution ◽  
Negative Cooperativity ◽  
Stem Loop ◽  
Smn Complex ◽  
Resolution Level ◽  
Structural Insights

ABSTRACTSm-class ribonucleoprotein particles (RNPs) are ring-shaped structures (Sm cores) formed by Sm hetero-heptamer around a segment of RNA, containing a nonameric oligoribonucleotide, PuAUUUNUGPu, followed by a stem-loop, and are basic structural modules critical for stability and functions of spliceosomal, telomerase and U7 RNPs. In the chaperones-assisted Sm core assembly, Gemin2 of the SMN complex, not only binds SmD1/D2/F/E/G (5Sm), but also serves as a checkpoint via a negative cooperativity mechanism uncovered in our recent study: Gemin2 constricts the horseshoe-shaped 5Sm in a narrow conformation from outside, preventing non-cognate RNA and SmD3/B from joining; only cognate RNA can bind inside 5Sm and widen 5Sm, dissociating Gemin2 from 5Sm and recruiting SmD3/B. However, the structural mechanics is unknown. Here I describe a coordinate-improved structure of 5Sm bound by Gemin2/SMN. Moreover, via new analysis, comparison of this structure with those of newly coordinate-improved Sm cores reveals the negative cooperativity mechanism between Gemin2 and RNA in binding 5Sm at atomic resolution level and provides structural insights into RNA selection and Gemin2’s release in Sm core assembly. Finally, implications in the evolution of the Sm-core assembly chaperoning machinery and the neurodegenerative disease spinal muscular atrophy caused by SMN deficiency are discussed.

scholarly journals Negative Cooperativity between Gemin2 and RNA provides Insights into RNA Selection and the SMN Complex’s Release in snRNP Assembly

2018 ◽  
Author(s):  
Hongfei Yi ◽  
Li Mu ◽  
Congcong Shen ◽  
Xi Kong ◽  
Yingzhi Wang ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Muscular Atrophy ◽  
Basic Mechanism ◽  
Negative Cooperativity ◽  
Sm Proteins ◽  
Early Step ◽  
Smn Complex ◽  
Narrow State ◽  
Snrnp Core

ABSTRACTThe assembly of snRNP cores, in which seven Sm proteins, D1/D2/F/E/G/D3/B, form a ring around the nonameric Sm site of snRNAs, is the early step of spliceosome formation and essential to eukaryotes. It is mediated by the PMRT5 and SMN complexes sequentially in vivo. SMN deficiency causes neurodegenerative disease spinal muscular atrophy (SMA). How the SMN complex assembles snRNP cores is largely unknown, especially how the SMN complex achieves high RNA assembly specificity and how it is released. Here we show, using crystallographic and biochemical approaches, that Gemin2 of the SMN complex enhances RNA specificity of SmD1/D2/F/E/G via a negative cooperativity between Gemin2 and RNA in binding SmD1/D2/F/E/G. Gemin2, independent of its N-tail, constrains the horseshoe-shaped SmD1/D2/F/E/G from outside in a physiologically relevant, narrow state, enabling high RNA specificity. Moreover, the assembly of RNAs inside widens SmD1/D2/F/E/G, causes the release of Gemin2/SMN allosterically and allows SmD3/B to join. The assembly of SmD3/B further facilitates the release of Gemin2/SMN. This is the first to show negative cooperativity in snRNP assembly, which provides insights into RNA selection and the SMN complex’s release. These findings reveal a basic mechanism of snRNP core assembly and facilitate pathogenesis studies of SMA.

scholarly journals Negative cooperativity between Gemin2 and RNA provides insights into RNA selection and the SMN complex's release in snRNP assembly

2019 ◽  
Vol 48 (2) ◽  
pp. 895-911 ◽  
Author(s):  
Hongfei Yi ◽  
Li Mu ◽  
Congcong Shen ◽  
Xi Kong ◽  
Yingzhi Wang ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Muscular Atrophy ◽  
Basic Mechanism ◽  
Negative Cooperativity ◽  
Sm Proteins ◽  
Early Step ◽  
Smn Complex ◽  
Narrow State ◽  
Snrnp Core

Abstract The assembly of snRNP cores, in which seven Sm proteins, D1/D2/F/E/G/D3/B, form a ring around the nonameric Sm site of snRNAs, is the early step of spliceosome formation and essential to eukaryotes. It is mediated by the PMRT5 and SMN complexes sequentially in vivo. SMN deficiency causes neurodegenerative disease spinal muscular atrophy (SMA). How the SMN complex assembles snRNP cores is largely unknown, especially how the SMN complex achieves high RNA assembly specificity and how it is released. Here we show, using crystallographic and biochemical approaches, that Gemin2 of the SMN complex enhances RNA specificity of SmD1/D2/F/E/G via a negative cooperativity between Gemin2 and RNA in binding SmD1/D2/F/E/G. Gemin2, independent of its N-tail, constrains the horseshoe-shaped SmD1/D2/F/E/G from outside in a physiologically relevant, narrow state, enabling high RNA specificity. Moreover, the assembly of RNAs inside widens SmD1/D2/F/E/G, causes the release of Gemin2/SMN allosterically and allows SmD3/B to join. The assembly of SmD3/B further facilitates the release of Gemin2/SMN. This is the first to show negative cooperativity in snRNP assembly, which provides insights into RNA selection and the SMN complex's release. These findings reveal a basic mechanism of snRNP core assembly and facilitate pathogenesis studies of SMA.

scholarly journals The Survival of Motor Neurons Protein Determines the Capacity for snRNP Assembly: Biochemical Deficiency in Spinal Muscular Atrophy

2005 ◽  
Vol 25 (13) ◽  
pp. 5543-5551 ◽  
Author(s):  
Lili Wan ◽  
Daniel J. Battle ◽  
Jeongsik Yong ◽  
Amelie K. Gubitz ◽  
Stephen J. Kolb ◽  
...  
Keyword(s):  
Spinal Muscular Atrophy ◽  
Motor Neurons ◽  
Muscular Atrophy ◽  
Protein Levels ◽  
Small Nuclear Ribonucleoprotein ◽  
Cell Extracts ◽  
Smn Complex ◽  
Survival Of Motor Neurons ◽  
Smn Protein ◽  
Nuclear Ribonucleoprotein

ABSTRACT Reduction of the survival of motor neurons (SMN) protein levels causes the motor neuron degenerative disease spinal muscular atrophy, the severity of which correlates with the extent of reduction in SMN. SMN, together with Gemins 2 to 7, forms a complex that functions in the assembly of small nuclear ribonucleoprotein particles (snRNPs). Complete depletion of the SMN complex from cell extracts abolishes snRNP assembly, the formation of heptameric Sm cores on snRNAs. However, what effect, if any, reduction of SMN protein levels, as occurs in spinal muscular atrophy patients, has on the capacity of cells to produce snRNPs is not known. To address this, we developed a sensitive and quantitative assay for snRNP assembly, the formation of high-salt- and heparin-resistant stable Sm cores, that is strictly dependent on the SMN complex. We show that the extent of Sm core assembly is directly proportional to the amount of SMN protein in cell extracts. Consistent with this, pulse-labeling experiments demonstrate a significant reduction in the rate of snRNP biogenesis in low-SMN cells. Furthermore, extracts of cells from spinal muscular atrophy patients have a lower capacity for snRNP assembly that corresponds directly to the reduced amount of SMN. Thus, SMN determines the capacity for snRNP biogenesis, and our findings provide evidence for a measurable deficiency in a biochemical activity in cells from patients with spinal muscular atrophy.

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