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Results for “ribonucleoprotein complexes”

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PubMed1973

A native ribonucleoprotein complex from Escherichia coli ribosomes.

An RNA-protein complex was isolated from the 50S subunit of E. coli ribosomes after trypsin digestion. The complex contains only one protein, L24. Treatment of the complex with pancreatic ribonuclease results in digestion of most of the RNA; however, an RNA fragment of about 100 nucleotides in length is stable to nuclease digestion and remains bound to the protein. It is also possible to reconstitute a complex from 23S RNA and isolated L24; nuclease digestion of this complex produces a resistant RNA fragment of the same size as the native complex. The protein can still bind to 23S RNA after N-methylation of about 20% of its lysine residues. Thus, by use of N-methylated L24 labeled with either (14)C or (3)H, the binding stoichiometry of the reconstituted complex was established; binding of L24 to RNA once again renders the protein trypsin-resistant. This would appear to be a good system for the study of RNA-protein interactions.

Bacterial Proteins↗
PubMed1998

The reverse transcriptase component of the Tetrahymena telomerase ribonucleoprotein complex.

Telomerase is a eukaryotic reverse transcriptase that adds simple sequence repeats to chromosome ends by copying a template sequence within the RNA component of the enzyme. We describe here the identification of a Tetrahymena telomerase protein with reverse transcriptase motifs, p133. This subunit is associated with the previously identified Tetrahymena telomerase RNA and the telomerase proteins p80 and p95 in immunoprecipitation assays. Therefore, all four known Tetrahymena telomerase components are present in a single complex. Expressed in rabbit reticulocyte lysate, recombinant p133 and telomerase RNA alone catalyze a reverse transcriptase activity with some similarities to and some differences from native Tetrahymena telomerase. These experiments suggest a complexity of telomerase structure and function.

Amino Acid Sequence↗
PubMed1992

Distribution of Cytosolic mRNAs Between Polysomal and Ribonucleoprotein Complex Fractions in Alfalfa Embryos : Stage-Specific Translational Repression of Storage Protein Synthesis during Early Somatic Embryo Development.

Cell-free translational and northern blot analyses were used to examine the distribution of storage protein messages in the cytoplasmic polysomal and mRNA-protein complex (mRNP) fractions during development of somatic and zygotic embryos of alfalfa (Medicago sativa cv Rangelander RL-34). No special array of messages was identified in the mRNP fraction; however, some messages were selectively enriched in either the polysome or mRNP fractions, and their distribution pattern varied quantitatively during development of the embryos. During the earliest stages of somatic embryo development, storage protein messages already were present, but there was no detectable accumulation of the proteins. Selective enrichment of messages for the 11S, 7S, and 2S storage proteins occurred in the mRNP fraction during the globular, heart, and torpedo stages of somatic embryogenesis, but the distribution pattern was shifted toward the polysomal fraction at the beginning of cotyledon development. Thus, there was translational repression of storage protein synthesis at the early stage of somatic embryo development that was relieved later. During the cotyledonary development stages in the somatic and zygotic embryos, storage protein synthesis and distribution of the messages were similar in that these specific messages were predominantly in the polysomal fraction.

Journal Article↗
PubMed2004

Identification of Staufen in the human immunodeficiency virus type 1 Gag ribonucleoprotein complex and a role in generating infectious viral particles.

Staufen is a host protein that is selectively incorporated into human immunodeficiency virus type 1 (HIV-1) particles in a poorly defined process that involves the selection of HIV-1 genomic RNA for encapsidation and the activity of its third double-stranded RNA-binding domain (dsRBD3). To better understand this, we characterized its interactions with pr55(Gag), the principal mediator of HIV-1 genomic RNA encapsidation. Chimeric proviruses harboring wild-type or mutant forms of Staufen were expressed in 293T cells. Cell fractionation analyses demonstrated that Staufen cosedimented with pr55(Gag) within detergent-resistant, trypsin-sensitive complexes that excluded mature capsid and matrix proteins. Coimmunoprecipitation and bioluminescence resonance energy transfer assays demonstrated a specific and direct interaction between Staufen and the nucleocapsid domain of pr55(Gag) in vitro and in live cells. This interaction is shown here to be mediated by Staufen's dsRBD3, with a contribution from its C-terminal domain. Immunoprecipitation and reverse transcription-PCR analyses showed that the 9-kb genomic RNA was found within Staufen-containing immune complexes. Spliced HIV-1 RNAs were not detected in these Staufen complexes, indicating a preferential association of Staufen with the 9-kb species. These results substantiate that Staufen and pr55(Gag) interact directly during HIV-1 expression. Knockdown of Staufen expression by small interfering RNAs in HIV-1-expressing cells demonstrated that this cellular protein was important for the generation of infectious virus. These data show that Staufen, pr55(Gag), and genomic RNA are part of the same intracellular complex and support a role for Staufen in pr55(Gag) function in viral assembly, genomic RNA encapsidation, and the generation of infectious viral particles.

Animals↗
PubMed1998

[26S-ribonucleoprotein complex (26S-proteasome) directly interacts with fibrillar actin].

26S-complex was purified from rat liver cells by centrifugation in sucrose gradients and ion exchange chromatography. The ability of 26S-proteasome to interact with fibrillar actin (F-actin) was examined by rapid cosidementation of these particles with F-actin in isokinetic sucrose gradients. It was shown that direct interaction occurred only at a low ATP concentration.

Actins↗
PubMed1999

Site-specific derivatization of RNA with photocrosslinkable groups.

Derivatization of RNA with heterobifunctional photocrosslinking reagents becomes an increasingly popular method for the analysis of structural properties of ribonucleoprotein complexes. This article describes a simple chemical modification-derivatization strategy used to introduce selected chemical groups at specific internal positions within the RNA ribose backbone. The strategy is based on the coupling of a haloacetyl adduct to a thiol residue in the phosphodiester bond. The use of a number of RNA probes derivatized with several different photoreactive groups can provide invaluable information on the structural distribution of components in complex ribonucleoprotein assemblies.

Azides↗
PubMed2002

Autoantigen microarrays for multiplex characterization of autoantibody responses.

We constructed miniaturized autoantigen arrays to perform large-scale multiplex characterization of autoantibody responses directed against structurally diverse autoantigens, using submicroliter quantities of clinical samples. Autoantigen microarrays were produced by attaching hundreds of proteins, peptides and other biomolecules to the surface of derivatized glass slides using a robotic arrayer. Arrays were incubated with patient serum, and spectrally resolvable fluorescent labels were used to detect autoantibody binding to specific autoantigens on the array. We describe and characterize arrays containing the major autoantigens in eight distinct human autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis. This represents the first report of application of such technology to multiple human disease sera, and will enable validated detection of antibodies recognizing autoantigens including proteins, peptides, enzyme complexes, ribonucleoprotein complexes, DNA and post-translationally modified antigens. Autoantigen microarrays represent a powerful tool to study the specificity and pathogenesis of autoantibody responses, and to identify and define relevant autoantigens in human autoimmune diseases.

Animals↗