scholarly journals Core spliceosomal Sm proteins as constituents of cytoplasmic mRNPs in plants

2020 ◽  
Vol 103 (3) ◽  
pp. 1155-1173
Author(s):  
Malwina Hyjek‐Składanowska ◽  
Mateusz Bajczyk ◽  
Marcin Gołębiewski ◽  
Przemysław Nuc ◽  
Agnieszka Kołowerzo‐Lubnau ◽  
...  
Keyword(s):  
Sm Proteins

Nuclear coiled bodies and the nucleolus

1994 ◽  
Vol 52 ◽  
pp. 20-21
Author(s):  
K. Brasch ◽  
J. Williams ◽  
D. Gallo ◽  
T. Lee ◽  
R. L. Ochs
Keyword(s):  
Mouse Liver ◽  
Nuclear Body ◽  
Nuclear Bodies ◽  
Model Systems ◽  
Coiled Body ◽  
Rrna Processing ◽  
Malignant Cells ◽  
Sm Proteins ◽  
Coiled Bodies ◽  
Unique Protein

Though first described in 1903 by Ramon-y-Cajal as silver-staining “accessory bodies” to nucleoli, nuclear bodies were subsequently rediscovered by electron microscopy about 30 years ago. Nuclear bodies are ubiquitous, but seem most abundant in hyperactive and malignant cells. The best studied type of nuclear body is the coiled body (CB), so termed due to characteristic morphology and content of a unique protein, p80-coilin (Fig.1). While no specific functions have as yet been assigned to CBs, they contain spliceosome snRNAs and proteins, and also the nucleolar protein fibrillarin. In addition, there is mounting evidence that CBs arise from or are generated near the nucleolus and then migrate into the nucleoplasm. This suggests that as yet undefined links may exist, between nucleolar pre-rRNA processing events and the spliceosome-associated Sm proteins in CBs.We are examining CB and nucleolar changes in three diverse model systems: (1) estrogen stimulated chick liver, (2) normal and neoplastic cells, and (3) polyploid mouse liver.

scholarly journals HOPS Proofreads the trans-SNARE Complex for Yeast Vacuole Fusion

2008 ◽  
Vol 19 (6) ◽  
pp. 2500-2508 ◽  
Author(s):  
Vincent J. Starai ◽  
Christopher M. Hickey ◽  
William Wickner
Keyword(s):  
Snare Complex ◽  
Wild Type ◽  
Fusion Event ◽  
Sm Proteins ◽  
Terminal Domain ◽  
Domain Structures ◽  
Vacuole Fusion ◽  
Protein Receptors ◽  
Optimal Fusion ◽  
Guanosine Triphosphatase

The fusion of yeast vacuoles, like other organelles, requires a Rab-family guanosine triphosphatase (Ypt7p), a Rab effector and Sec1/Munc18 (SM) complex termed HOPS (homotypic fusion and vacuole protein sorting), and soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). The central 0-layer of the four bundled vacuolar SNAREs requires the wild-type three glutaminyl (Q) and one arginyl (R) residues for optimal fusion. Alterations of this layer dramatically increase the Km value for SNAREs to assemble trans-SNARE complexes and to fuse. We now find that added purified HOPS complex strongly suppresses the fusion of vacuoles bearing 0-layer alterations, but it has little effect on the fusion of vacuoles with wild-type SNAREs. HOPS proofreads at two levels, inhibiting the formation of trans-SNARE complexes with altered 0-layers and suppressing the ability of these mismatched 0-layer trans-SNARE complexes to support membrane fusion. HOPS proofreading also extends to other parts of the SNARE complex, because it suppresses the fusion of trans-SNARE complexes formed without the N-terminal Phox homology domain of Vam7p (Qc). Unlike some other SM proteins, HOPS proofreading does not require the Vam3p (Qa) N-terminal domain. HOPS thus proofreads SNARE domain and N-terminal domain structures and regulates the fusion capacity of trans-SNARE complexes, only allowing full function for wild-type SNARE configurations. This is the most direct evidence to date that HOPS is directly involved in the fusion event.

Stoichiometry of the Sm proteins in yeast spliceosomal snRNPs supports the heptamer ring model of the core domain11Edited by T. Richmond

2001 ◽  
Vol 308 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Stefan Walke ◽  
Elisabeth Bragado-Nilsson ◽  
Bertrand Séraphin ◽  
Kiyoshi Nagai
Keyword(s):  
Sm Proteins ◽  
The Core ◽  
Ring Model

scholarly journals Pulmonary Artery (PA) Smooth Muscle (SM) Proteins in Postnatal Sheep with High Flow Pulmonary Hypertension (PH). ♦ 146

1997 ◽  
Vol 41 ◽  
pp. 27-27
Author(s):  
L Van Der Steeg ◽  
J Fineman ◽  
K E Kamm ◽  
S Chamnanvanakij ◽  
Y Arens ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
Smooth Muscle ◽  
Pulmonary Artery ◽  
High Flow ◽  
Sm Proteins

scholarly journals snRNP: Rich Nuclear Bodies inHyacinthus orientalisL. Microspores and Developing Pollen Cells

2009 ◽  
Vol 2009 ◽  
pp. 1-12 ◽  
Author(s):  
K. Zienkiewicz ◽  
E. Bednarska
Keyword(s):  
Pollen Development ◽  
Rna Synthesis ◽  
Generative Cell ◽  
Pollen Grains ◽  
Strong Relationship ◽  
Nuclear Bodies ◽  
Cajal Body ◽  
Sm Proteins ◽  
Hyacinthus Orientalis

The aim of the present work was the characterization of nuclear bodies in the microspore and developing pollen cells ofHyacinthus orientalisL.. The combination of Ag-NOR, immunofluorescence and immunogold techniques was used in this study. The obtained results showed the presence of highly agyrophylic extranucleolar bodies in microspore and developing pollen cells, which were finally identified as Cajal bodies. In all cases, a strong accumulation of snRNP-indicating molecules including TMG cap, Sm proteins and U2 snRNA, was observed in the examined nuclear bodies. In contrast to their number the size of the identified structures did not change significantly during pollen development. In the microspore and the vegetative cell of pollen grains CBs were more numerous than in the generative cell. At later stages of pollen development, a drastic decrease in CB number was observed and, just before anthesis, a complete lack of these structures was indicated in both pollen nuclei. On the basis of these results, as well as our previous studies, we postulate a strong relationship between Cajal body numbers and the levels of RNA synthesis and splicing machinery elements in microspore and developing pollen cells.

scholarly journals Sec17 (α-SNAP) and Sec18 (NSF) restrict membrane fusion to R-SNAREs, Q-SNAREs, and SM proteins from identical compartments

2019 ◽  
Vol 116 (47) ◽  
pp. 23573-23581
Author(s):  
Youngsoo Jun ◽  
William Wickner
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Fusion ◽  
Protein Complex ◽  
Negative Regulation ◽  
Rab Gtpases ◽  
Sm Proteins ◽  
Rab Family ◽  
Sm Protein

Membrane fusion at each organelle requires conserved proteins: Rab-GTPases, effector tethering complexes, Sec1/Munc18 (SM)-family SNARE chaperones, SNAREs of the R, Qa, Qb, and Qc families, and the Sec17/α-SNAP and ATP-dependent Sec18/NSF SNARE chaperone system. The basis of organelle-specific fusion, which is essential for accurate protein compartmentation, has been elusive. Rab family GTPases, SM proteins, and R- and Q-SNAREs may contribute to this specificity. We now report that the fusion supported by SNAREs alone is both inefficient and promiscuous with respect to organelle identity and to stimulation by SM family proteins or complexes. SNARE-only fusion is abolished by the disassembly chaperones Sec17 and Sec18. Efficient fusion in the presence of Sec17 and Sec18 requires a tripartite match between the organellar identities of the R-SNARE, the Q-SNAREs, and the SM protein or complex. The functions of Sec17 and Sec18 are not simply negative regulation; they stimulate fusion with either vacuolar SNAREs and their SM protein complex HOPS or endoplasmic reticulum/cis-Golgi SNAREs and their SM protein Sly1. The fusion complex of each organelle is assembled from its own functionally matching pieces to engage Sec17/Sec18 for fusion stimulation rather than inhibition.

scholarly journals Structurally related but functionally distinct yeast Sm D core small nuclear ribonucleoprotein particle proteins.

1995 ◽  
Vol 15 (1) ◽  
pp. 445-455 ◽  
Author(s):  
J Roy ◽  
B Zheng ◽  
B C Rymond ◽  
J L Woolford
Keyword(s):  
Protein Complexes ◽  
Mrna Splicing ◽  
Yeast Cells ◽  
Ribonucleoprotein Particle ◽  
Sm Proteins ◽  
Small Nuclear Ribonucleoprotein ◽  
Snrnp Protein ◽  
Nuclear Ribonucleoprotein ◽  
Precursor Mrna

Spliceosome assembly during pre-mRNA splicing requires the correct positioning of the U1, U2, U4/U6, and U5 small nuclear ribonucleoprotein particles (snRNPs) on the precursor mRNA. The structure and integrity of these snRNPs are maintained in part by the association of the snRNAs with core snRNP (Sm) proteins. The Sm proteins also play a pivotal role in metazoan snRNP biogenesis. We have characterized a Saccharomyces cerevisiae gene, SMD3, that encodes the core snRNP protein Smd3. The Smd3 protein is required for pre-mRNA splicing in vivo. Depletion of this protein from yeast cells affects the levels of U snRNAs and their cap modification, indicating that Smd3 is required for snRNP biogenesis. Smd3 is structurally and functionally distinct from the previously described yeast core polypeptide Smd1. Although Smd3 and Smd1 are both associated with the spliceosomal snRNPs, overexpression of one cannot compensate for the loss of the other. Thus, these two proteins have distinct functions. A pool of Smd3 exists in the yeast cytoplasm. This is consistent with the possibility that snRNP assembly in S. cerevisiae, as in metazoans, is initiated in the cytoplasm from a pool of RNA-free core snRNP protein complexes.

scholarly journals A Novel WD Repeat Protein Component of the Methylosome Binds Sm Proteins

2001 ◽  
Vol 277 (10) ◽  
pp. 8243-8247 ◽  
Author(s):  
Westley J. Friesen ◽  
Anastasia Wyce ◽  
Sergey Paushkin ◽  
Linda Abel ◽  
Juri Rappsilber ◽  
...  
Keyword(s):  
Protein Component ◽  
Sm Proteins ◽  
Repeat Protein ◽  
Wd Repeat

scholarly journals The Sec1p/Munc18 protein Vps45p binds its cognate SNARE proteins via two distinct modes

2006 ◽  
Vol 173 (6) ◽  
pp. 927-936 ◽  
Author(s):  
Lindsay N. Carpp ◽  
Leonora F. Ciufo ◽  
Scott G. Shanks ◽  
Alan Boyd ◽  
Nia J. Bryant
Keyword(s):  
Crystal Structure ◽  
Membrane Trafficking ◽  
Protein Family ◽  
Snare Proteins ◽  
Outer Face ◽  
Sm Proteins ◽  
Hydrophobic Pocket ◽  
Second Mode ◽  
Sm Protein ◽  
Domain I

Sec1p/Munc18 (SM) proteins are essential for SNARE-mediated membrane trafficking. The formulation of unifying hypotheses for the function of the SM protein family has been hampered by the observation that two of its members bind their cognate syntaxins (Sxs) in strikingly different ways. The SM protein Vps45p binds its Sx Tlg2p in a manner analogous to that captured by the Sly1p–Sed5p crystal structure, whereby the NH2-terminal peptide of the Sx inserts into a hydrophobic pocket on the outer face of domain I of the SM protein. In this study, we report that although this mode of interaction is critical for the binding of Vps45p to Tlg2p, the SM protein also binds Tlg2p-containing SNARE complexes via a second mode that involves neither the NH2 terminus of Tlg2p nor the region of Vps45p that facilitates this interaction. Our findings point to the possibility that SM proteins interact with their cognate SNARE proteins through distinct mechanisms at different stages in the SNARE assembly/disassembly cycle.

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