Periodic expression of Sm proteins parallels formation of nuclear Cajal bodies and cytoplasmic snRNP-rich bodies

Abstract

Small nuclear ribonucleoproteins (snRNPs) play a fundamental role in pre-mRNA processing in the nucleus. The biogenesis of snRNPs involves a sequence of events that occurs in both the nucleus and cytoplasm. Despite the wealth of biochemical information about the cytoplasmic assembly of snRNPs, little is known about the spatial organization of snRNPs in the cytoplasm. In the cytoplasm of larch microsporocytes, a cyclic appearance of bodies containing small nuclear RNA (snRNA) and Sm proteins was observed during anther meiosis. We observed a correlation between the occurrence of cytoplasmic snRNP bodies, the levels of Sm proteins, and the dynamic formation of Cajal bodies. Larch microsporocytes were used for these studies. This model is characterized by natural fluctuations in the level of RNA metabolism, in which periods of high transcriptional activity are separated from periods of low transcriptional activity. In designing experiments, the authors considered the differences between the nuclear and cytoplasmic phases of snRNP maturation and generated a hypothesis about the direct participation of Sm proteins in a molecular switch triggering the formation of Cajal bodies.Electronic supplementary materialThe online version of this article (doi:10.1007/s00418-011-0861-8) contains supplementary material, which is available to authorized users.

Reorganization of Cajal bodies and nucleolar targeting of coilin in motor neurons of type I spinal muscular atrophy

“…In this view, the formation of a single canonical CB in many SMA motor neurons may result from the reduced amount of SMN protein, which, in all likelihood, represents a limiting factor for the CB assembly. The decrease in the number of canonical CBs may reduce the eYciency of snRNP assembly reactions that occur in these nuclear compartments (Matera et al 2009;Smolinski et al 2011), resulting in a severe dysfunction of pre-mRNA splicing in motor neurons. Interestingly, canonical CBs are conspicuously absent in the majority of motor neurons in an advanced stage of neuronal degeneration with marked chromatolysis and eccentric nuclei.…”

Regulation of poly(A) RNA retention in the nucleus as a survival strategy of plants during hypoxia

“…20,21 Thus, the marker for Cajal bodies in plants, except for coilin, are proteins associated with snRNA, such as Sm or U2B'. 22,23,24 Accordingly, in this work, we determined the subcellular localisations and analyzed the quantity of poly(A) RNA, along with a few transcripts of protein coding genes, in cells before and during hypoxia and after the removal of stress conditions in Lupinus luteus and Arabidopsis thaliana. We also established the levels of the elongation form of RNA polymerase II and the distribution of splicing factors.…”

Core spliceosomal Sm proteins as constituents of cytoplasmic mRNPs in plants

“…As stated in recent literature, a vast majority of mRNA posttranscriptional regulation occurs within the specialized microdomains referred to as cytoplasmic bodies 6,7 . These nonmembrane bound, highly dynamic structures enriched in ribonucleoproteins are evolutionarily conserved, as their occurrence has been confirmed in yeasts 7,8 , protozoans 9 , nematodes 10,11 , insects 12,13 , amphibians 14 , mammals 15,16 , and plants [17][18][19][20] . Several cytoplasmic bodies have been described to date, including P-bodies, stress granules, neuronal granules, germinal granules and nuage, among others.…”

“…As stated in recent literature, a vast majority of mRNA posttranscriptional regulation occurs within the specialized microdomains referred to as cytoplasmic bodies 6,7 . These nonmembrane bound, highly dynamic structures enriched in ribonucleoproteins are evolutionarily conserved, as their occurrence has been confirmed in yeasts 7,8 , protozoans 9 , nematodes 10,11 , insects 12,13 , amphibians 14 , mammals 15,16 , and plants [17][18][19][20] . Several cytoplasmic bodies have been described to date, including P-bodies, stress granules, neuronal granules, germinal granules and nuage, among others.The core cytoplasmic bodies in eukaryotic cells are P-bodies, which are sites of mRNA regulation, including 5'-3' deadenylation-dependent degradation 8,21 , miRNA-mediated decay 16 , and mRNA stabilization and sequestration 17 , as well as nonsense-mediated decay (NMD) 22 , and translational regulation [23][24][25][26] .…”