Novotny I, Podolská K, Blazíková M, Valásek LS, Svoboda P, Stanek D. Nuclear LSm8 affects number of cytoplasmic processing bodies via controlling cellular distribution of Like-Sm proteins.
Mol Biol Cell 2012;
23:3776-85. [PMID:
22875987 PMCID:
PMC3459855 DOI:
10.1091/mbc.e12-02-0085]
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Abstract
We show that depletion of nuclear Like-Sm 8 (LSm8) dramatically increases processing body (P-body) number, provide the explanation that LSm8 acts via the alteration of the nuclear–cytoplasmic distribution of LSm2–7 proteins, and propose a model that P-bodies form via self-organization.
Processing bodies (P-bodies) are dynamic cytoplasmic structures involved in mRNA degradation, but the mechanism that governs their formation is poorly understood. In this paper, we address a role of Like-Sm (LSm) proteins in formation of P-bodies and provide evidence that depletion of nuclear LSm8 increases the number of P-bodies, while LSm8 overexpression leads to P-body loss. We show that LSm8 knockdown causes relocalization of LSm4 and LSm6 proteins to the cytoplasm and suggest that LSm8 controls nuclear accumulation of all LSm2–7 proteins. We propose a model in which redistribution of LSm2–7 to the cytoplasm creates new binding sites for other P-body components and nucleates new, microscopically visible structures. The model is supported by prolonged residence of two P-body proteins, DDX6 and Ago2, in P-bodies after LSm8 depletion, which indicates stronger interactions between these proteins and P-bodies. Finally, an increased number of P-bodies has negligible effects on microRNA-mediated translation repression and nonsense mediated decay, further supporting the view that the function of proteins localized in P-bodies is independent of visible P-bodies.
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