Intracellular distribution of the U1A protein depends on active transport and nuclear binding to U1 snRNA.

Nuclear transport of the U1 snRNP-specific protein U1A has been examined. U1A moves to the nucleus by an active process which is independent of interaction with U1 snRNA. Nuclear localization requires an unusually large sequence element situated between amino acids 94 and 204 of the protein. U1A transport is not unidirectional. The protein shuttles between nucleus and cytoplasm. At equilibrium, the concentration of the protein in the nucleus and cytoplasm is not, however, determined solely by transport rates, but can be perturbed by introducing RNA sequences that can specifically bind U1A in either the nuclear or cytoplasmic compartment. Thus, U1A represents a novel class of protein which shuttles between cytoplasm and nucleus and whose intracellular distribution can be altered by the number of free binding sites for the protein present in the cytoplasm or the nucleus.

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Multiple domains of U1 snRNA, including U1 specific protein binding sites, are required for splicing.

The EMBO Journal ◽

10.1002/j.1460-2075.1990.tb08231.x ◽

1990 ◽

Vol 9 (4) ◽

pp. 1237-1244 ◽

Cited By ~ 21

Author(s):

J. Hamm ◽

N.A. Dathan ◽

D. Scherly ◽

I.W. Mattaj

Keyword(s):

Protein Binding ◽

Binding Sites ◽

Specific Protein ◽

Protein Binding Sites ◽

U1 Snrna ◽

Multiple Domains

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EVALUATION OF TISSUE STEROID BINDING IN VITRO

Acta Endocrinologica ◽

10.1530/acta.0.068s223 ◽

1971 ◽

Vol 68 (1_Suppl) ◽

pp. S223-S246 ◽

Cited By ~ 2

Author(s):

C. R. Wira ◽

H. Rochefort ◽

E. E. Baulieu

Keyword(s):

Protein Binding ◽

Binding Sites ◽

Experimental System ◽

Specific Protein ◽

Coupling Mechanism ◽

Target Tissue ◽

Protein Binding Sites ◽

Definition Of ◽

Hormone Specificity

ABSTRACT The definition of a RECEPTOR* in terms of a receptive site, an executive site and a coupling mechanism, is followed by a general consideration of four binding criteria, which include hormone specificity, tissue specificity, high affinity and saturation, essential for distinguishing between specific and nonspecific binding. Experimental approaches are proposed for choosing an experimental system (either organized or soluble) and detecting the presence of protein binding sites. Techniques are then presented for evaluating the specific protein binding sites (receptors) in terms of the four criteria. This is followed by a brief consideration of how receptors may be located in cells and characterized when extracted. Finally various examples of oestrogen, androgen, progestagen, glucocorticoid and mineralocorticoid binding to their respective target tissues are presented, to illustrate how researchers have identified specific corticoid and mineralocorticoid binding in their respective target tissue receptors.

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On the dynamics of some small structural motifs in rRNA upon ligand binding

Journal of the Serbian Chemical Society ◽

10.2298/jsc0801041r ◽

2008 ◽

Vol 73 (1) ◽

pp. 41-53

Author(s):

Aleksandra Rakic ◽

Petar Mitrasinovic

Keyword(s):

Molecular Dynamics ◽

Conformational Changes ◽

Binding Sites ◽

De Novo ◽

Reference Structure ◽

Base Pairs ◽

Rna Sequences ◽

Conformational Model ◽

Thermodynamic Variables ◽

Dynamics Simulations

The present study characterizes using molecular dynamics simulations the behavior of the GAA (1186-1188) hairpin triloops with their closing c-g base pairs in large ribonucleoligand complexes (PDB IDs: 1njn, 1nwy, 1jzx). The relative energies of the motifs in the complexes with respect to that in the reference structure (unbound form of rRNA; PDB ID: 1njp) display the trends that agree with those of the conformational parameters reported in a previous study1 utilizing the de novo pseudotorsional (?,?) approach. The RNA regions around the actual RNA-ligand contacts, which experience the most substantial conformational changes upon formation of the complexes were identified. The thermodynamic parameters, based on a two-state conformational model of RNA sequences containing 15, 21 and 27 nucleotides in the immediate vicinity of the particular binding sites, were evaluated. From a more structural standpoint, the strain of a triloop, being far from the specific contacts and interacting primarily with other parts of the ribosome, was established as a structural feature which conforms to the trend of the average values of the thermodynamic variables corresponding to the three motifs defined by the 15-, 21- and 27-nucleotide sequences. From a more functional standpoint, RNA-ligand recognition is suggested to be presumably dictated by the types of ligands in the complexes.

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Nuclear transport of the U2 snRNP-specific U2B'' protein is mediated by both direct and indirect signalling mechanisms

Journal of Cell Science ◽

10.1242/jcs.107.7.1807 ◽

1994 ◽

Vol 107 (7) ◽

pp. 1807-1816 ◽

Cited By ~ 1

Author(s):

C. Kambach ◽

I.W. Mattaj

Keyword(s):

Nuclear Localization ◽

Nuclear Import ◽

Nuclear Localization Signal ◽

Nuclear Transport ◽

U2 Snrna ◽

Central Segment ◽

U2 Snrnp ◽

U1 Snrnp ◽

Localization Signal ◽

Protein Amino Acids

Experiments investigating the nuclear import of the U2 snRNP-specific B'' protein (U2B'') are presented. U2B'' nuclear transport is shown to be able to occur independently of binding to U2 snRNA. The central segment of the protein (amino acids 90–146) encodes an unusual nuclear localization signal (NLS) that is related to that of the U1 snRNP-specific A protein. However, nuclear import of U2B'' does not depend on this NLS. Sequences in the N-terminal RNP motif of the protein are sufficient to direct nuclear transport, and evidence is presented that the interaction of U2B'' with the U2A' protein mediates this effect. This suggests that U2B'' can ‘piggy-back’ to the nucleus in association with U2A’, and thus be imported to the nucleus by two different mechanisms. U2A' nuclear transport, on the other hand, can occur independently of both U2B'' binding and of U2 snRNA.

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Intact Ca(2+)-binding sites are required for targeting of annexin 1 to endosomal membranes in living HeLa cells

Journal of Cell Science ◽

10.1242/jcs.113.22.3931 ◽

2000 ◽

Vol 113 (22) ◽

pp. 3931-3938 ◽

Cited By ~ 1

Author(s):

U. Rescher ◽

N. Zobiack ◽

V. Gerke

Keyword(s):

Hela Cells ◽

Binding Sites ◽

Fluorescent Protein ◽

Binding Protein ◽

Membrane Binding ◽

Growth Factor Receptor ◽

Intracellular Distribution ◽

Live Cells ◽

Membrane Structures ◽

Annexin 1

Annexin 1 is a Ca(2+)-regulated membrane binding protein and a major substrate of the epidermal growth factor receptor kinase. Because of its properties and intracellular distribution, the protein has been implicated in endocytic trafficking of the receptor, in particular in receptor sorting occurring in multivesicular endosomes. Up to now, however, the localization of annexin 1 to cellular membranes has been limited to subcellular fractionation and immunocytochemical analyses of fixed cells. To establish its localization in live cells, we followed the intracellular fate of annexin 1 molecules fused to the Green Fluorescent Protein (GFP). We show that annexin 1-GFP associates with distinct, transferrin receptor-positive membrane structures in living HeLa cells. A GFP chimera containing the Ca(2+)/phospholipid-binding protein core of annexin 1 also shows a punctate intracellular distribution, although the structures labeled here do not resemble early but, at least in part, late endosomes. In contrast, the cores of annexins 2 and 4 fused to GFP exhibit a cytoplasmic or a different punctate distribution, respectively, indicating that the highly homologous annexin core domains carry distinct membrane specificities within live cells. By inactivating the three high-affinity Ca(2+) binding sites in annexin 1 we also show that endosomal membrane binding of the protein in live HeLa cells depends on the integrity of these Ca(2+) binding sites. More detailed analysis identifies a single Ca(2+) site in the second annexin repeat that is crucially involved in establishing the membrane association. These results reveal for the first time that intracellular membrane binding of an annexin in living cells requires Ca(2+) and is mediated in part through an annexin core domain that is capable of establishing specific interactions.

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Intracellular distribution and polyadenylate content of adeno-associated virus RNA sequences

Virology ◽

10.1016/0042-6822(76)90080-5 ◽

1976 ◽

Vol 73 (1) ◽

pp. 273-285 ◽

Cited By ~ 9

Author(s):

Barrie J. Carter

Keyword(s):

Intracellular Distribution ◽

Rna Sequences ◽

Adeno Associated Virus ◽

Virus Rna

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Maximal Activity of an Erythroid-specific Enhancer Requires the Presence of Specific Protein Binding Sites in Linked Promoters

Journal of Biological Chemistry ◽

10.1074/jbc.273.22.13593 ◽

1998 ◽

Vol 273 (22) ◽

pp. 13593-13598 ◽

Cited By ~ 10

Author(s):

Persis J. Amrolia ◽

Wesley Gabbard ◽

John M. Cunningham ◽

Stephen M. Jane

Keyword(s):

Protein Binding ◽

Binding Sites ◽

Maximal Activity ◽

Specific Protein ◽

Protein Binding Sites

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Phylogenetic Comparison and Splicing Analysis of the U1 snRNP-specific Protein U1C in Eukaryotes

Frontiers in Molecular Biosciences ◽

10.3389/fmolb.2021.696319 ◽

2021 ◽

Vol 8 ◽

Author(s):

Kai-Lu Zhang ◽

Jian-Li Zhou ◽

Jing-Fang Yang ◽

Yu-Zhen Zhao ◽

Debatosh Das ◽

...

Keyword(s):

Gene Family ◽

Cancer Progression ◽

Expression Profiles ◽

Expression Patterns ◽

Specific Protein ◽

Comprehensive Overview ◽

Small Nuclear Ribonucleoprotein ◽

U1 Snrnp ◽

Multiple Copies ◽

And Function

As a pivotal regulator of 5’ splice site recognition, U1 small nuclear ribonucleoprotein (U1 snRNP)-specific protein C (U1C) regulates pre-mRNA splicing by interacting with other components of the U1 snRNP complex. Previous studies have shown that U1 snRNP and its components are linked to a variety of diseases, including cancer. However, the phylogenetic relationships and expression profiles of U1C have not been studied systematically. To this end, we identified a total of 110 animal U1C genes and compared them to homologues from yeast and plants. Bioinformatics analysis shows that the structure and function of U1C proteins is relatively conserved and is found in multiple copies in a few members of the U1C gene family. Furthermore, the expression patterns reveal that U1Cs have potential roles in cancer progression and human development. In summary, our study presents a comprehensive overview of the animal U1C gene family, which can provide fundamental data and potential cues for further research in deciphering the molecular function of this splicing regulator.

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A block in mammalian splicing occurring after formation of large complexes containing U1, U2, U4, U5, and U6 small nuclear ribonucleoproteins

Molecular and Cellular Biology ◽

10.1128/mcb.9.1.259-267.1989 ◽

1989 ◽

Vol 9 (1) ◽

pp. 259-267

Author(s):

C H Agris ◽

M E Nemeroff ◽

R M Krug

Keyword(s):

Specific Protein ◽

Viral Mrna ◽

Sequence Element ◽

Time Points ◽

Total Absence ◽

Nuclear Extracts ◽

Infected Cells ◽

Small Nuclear Ribonucleoproteins ◽

Rna Precursor

The assembly of mammalian pre-mRNAs into large 50S to 60S complexes, or spliceosomes, containing small nuclear ribonucleoproteins (snRNPs) leads to the production of splicing intermediates, 5' exon and lariat-3' exon, and the subsequent production of spliced products. Influenza virus NS1 mRNA, which encodes a virus-specific protein, is spliced in infected cells to form another viral mRNA (the NS2 mRNA), such that the ratio of unspliced to spliced mRNA is 10 to 1. NS1 mRNA was not detectably spliced in vitro with nuclear extracts from uninfected HeLa cells. Surprisingly, despite the almost total absence of splicing intermediates in the in vitro reaction, NS1 mRNA very efficiently formed ATP-dependent 55S complexes. The formation of 55S complexes with NS1 mRNA was compared with that obtained with an adenovirus pre-mRNA (pKT1 transcript) by using partially purified splicing fractions that restricted the splicing of the pKT1 transcript to the production of splicing intermediates. At RNA precursor levels that were considerably below saturation, approximately 10-fold more of the input NS1 mRNA than of the input pKT1 transcript formed 55S complexes at all time points examined. The pKT1 55S complexes contained splicing intermediates, whereas the NS1 55S complexes contained only precursor NS1 mRNA. Biotin-avidin affinity chromatography showed that the 55S complexes formed with either NS1 mRNA or the pKT1 transcript contained the U1, U2, U4, U5, and U6 snRNPs. Consequently, the formation of 55S complexes containing these five snRNPs was not sufficient for the catalysis of the first step of splicing, indicating that some additional step(s) needs to occur subsequent to this binding. These results indicate that the 5' splice site, 3' and branch point of NS1 and mRNA were capable of interacting with the five snRNPs to form 55S complexes, but apparently some other sequence element(s) in NS1 mRNA blocked the resolution of the 55S complexes that leads to the catalysis of splicing. On the basis of our results, we suggest mechanisms by which the splicing of NS1 is controlled in infected cells.

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