Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An RNA-binding protein gene (rbp1) from Drosophila melanogaster, encoding an RNA recognition motif and an Arg-Ser rich (RS) domain, has been characterized. The predicted amino acid sequence of rbp1 is similar to those of the human splicing factor ASF/SF2, the Drosophila nuclear phosphoprotein SRp55, and the Drosophila puff-associated protein B52. Northern and immunohistochemical analyses showed that rbp1 is expressed at all stages in all tissues and that the RBP1 protein is localized to the nucleus. Consistent with a role in mRNA metabolism, indirect immunofluorescence reveals that the RBP1 protein colocalizes with RNA polymerase II on larval salivary gland polytene chromosomes. RBP1 protein made in Escherichia coli was tested for splicing activity using human cell extracts in which ASF has been shown previously both to activate splicing and to affect the choice of splice sites in alternatively spliced pre-mRNAs. In these assays, RBP1 protein, like ASF, is capable of both activating splicing and switching splice site selection. However, in each case, clear differences in the behavior of the two proteins were detected, suggesting that they have related but not identical functions. The general nuclear expression pattern, colocalization on chromosomes with RNA polymerase II, the similarity to ASF/SF2, SRp55, and B52, along with the effect on alternative splicing shown in vitro, suggest that rbp1 is involved in the processing of precursor mRNAs.
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PMID:The Drosophila RNA-binding protein RBP1 is localized to transcriptionally active sites of chromosomes and shows a functional similarity to human splicing factor ASF/SF2. 134 Apr 70

The plus strand of the L-A double-stranded RNA virus of Saccharomyces cerevisiae has two large open reading frames, ORF1, which encodes the major coat protein, and ORF2, which encodes a single-stranded RNA-binding protein having a sequence diagnostic of viral RNA-dependent RNA polymerases. ORF2 is expressed only as a Gag-Pol-type fusion protein with ORF1. We have constructed a plasmid which expresses these proteins from the yeast PGK1 promoter. We show that this plasmid can support the replication of the killer toxin-encoding M1 satellite virus in the absence of an L-A double-stranded RNA helper virus itself. This requires ORF2 expression, providing a potential in vivo assay for the RNA polymerase and single-stranded RNA-binding activities of the fusion protein determined by ORF2. ORF1 expression, like a host ski- mutation, can suppress the usual requirement of M1 for the MAK11, MAK18, and MAK27 genes and allow a defective L-A (L-A-E) to support M1 replication. These results suggest that expression of ORF1 from the vector makes the cell a ski- phenocopy. Indeed, expression of ORF1 in a wild-type killer makes it a superkiller, suggesting that a target of the SKI antiviral system may be the major coat protein.
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PMID:Expression of yeast L-A double-stranded RNA virus proteins produces derepressed replication: a ski- phenocopy. 198 95

Autoantibodies from systemic rheumatic disorders have become useful reagents in molecular biology. SS-B/La, a major target of autoantibodies in lupus and Sjogren's syndrome, has been identified as a 46 kDa protein component of a ribonucleoprotein (RNP) particle implicated in the maturation of RNA polymerase III transcripts. This report describes the complete sequences of human and bovine SS-B/La and the identification of RNA-binding protein consensus sequences RNP1 and RNP2 in the N-terminal region previously shown to be complexed with RNA in UV-crosslinking experiments. Segments of about 95 residues from the RNA-binding domain of SS-B/La and from 29 RNA-binding domains of several other proteins are analysed with respect to the frequency of amino acids and their hydrophobicity at each position. The data suggest that SS-B/La belongs to a large family of RNA-binding proteins which includes heterogeneous nuclear RNPs, nucleolin, mRNA polyadenylate binding protein, and small nuclear RNPs.
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PMID:Ribonucleoprotein SS-B/La belongs to a protein family with consensus sequences for RNA-binding. 246 31

La is an autoimmune RNA-binding protein of 47 kDa that plays a role in the transcription of RNA polymerase III. Both genomic and complementary DNAs were isolated that encompass the coding sequence of the human La molecule. The genomic clones encompass 11 exons and a putative G/C-rich promoter upstream of the mRNA start site. The cDNA sequence encodes a protein of 408 amino acids and can be divided into two structural domains based upon amino acid content and protease sensitivity. An unusually long stretch of 130 amino acids, much of which was predicted to form a stable alpha-helix, was found near the middle of the protein between the two domains. A ribonucleoprotein (RNP) consensus sequence was found just NH2-terminal to the long alpha-helix. The RNP consensus sequence is split into two exons by the fifth intron. Expression of three separate fragments of the La protein in Escherichia coli showed that a strongly autoimmune-reactive portion resides in the fragment containing the RNP consensus sequence and most of the long alpha-helical core. Autoantibodies from La patients also reacted with the terminal regions of the protein, but the extent of reactivity varied among patients. Differences in reactivity of autoantibodies to each portion of La protein may reflect an evolution of recognition of different epitopes during the development of the autoimmune response. These findings support an antigen-driven mechanism for autoimmune reactivity.
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PMID:Genomic structure and amino acid sequence domains of the human La autoantigen. 319 25

RNA polymerase III transcription can be inhibited in vitro by two sera from patients with autoimmune diseases. The first serum, designated anti-SS-B (or La), has antibodies directed against a 50,000 dalton polypeptide that is part of a larger ribonucleoprotein complex. The second serum, designated anti-SpNo, recognizes a target antigen polypeptide of greater than 100,000 daltons as well as the SS-B antigen. Both sera selectively remove required transcription factors from the transcription extract, and inhibition can be rescued by the addition of a HeLa S100 extract to the depleted transcription system. The HeLa S100 extract was sequentially fractionated by ion-exchange chromatography on DEAE-cellulose and phosphocellulose. The high salt eluate from the latter column was also able to rescue the anti-SS-B inhibition as was the immunoaffinity-purified SS-B ribonucleoprotein complex isolated from HeLa, Xenopus or rabbit thymus. Immunoblots of the active fractions indicated that all contained the SS-B immunoreactive polypeptide, but probes of replica filters for DNA-binding suggested that the transcription factor is not the SS-B antigen but a 64,000 dalton polypeptide component of the antigen ribonucleoprotein complex. SS-B is itself an RNA-binding protein and could be shown to bind nascent 5S RNA transcripts in vitro. Differential ammonium sulfate precipitation and DNA cellulose chromatography has confirmed that a group of 64-68 K dalton polypeptides are components of the SS-B ribonucleoprotein complex associated with transcription factor activity.
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PMID:Association of an RNA polymerase III transcription factor with a ribonucleoprotein complex recognized by autoimmune sera. 623 2

Protein H16, which we have identified previously in mammalian cell lines, binds in vitro to two single stranded DNA sites on the late strand of the early promoter of SV40. It has no other single strand binding site in the SV40 genome and does not bind to double stranded DNA. In vitro, H16 can be shown to stimulate strongly the activity of purified RNA polymerase II. Here we have purified this 70 kDa protein from cultured monkey cells and have sequenced three of its tryptic peptides. The analysis indicates that H16 is the simian homolog of human protein K, a nuclear RNA-binding protein found in heterogeneous nuclear ribonucleoprotein (hnRNP) particles, which contains a KH domain present in several proteins including the fragile X mental retardation gene product (FMR1). The binding affinities of protein K/H16 for RNA and DNA were subsequently compared in detail. They showed that under conditions where K/H16 binds strongly to its single stranded DNA site, it binds very weakly to the corresponding RNA sequence. This result suggests a possible shuttling of the protein from RNA to DNA during processes which involve opening of the DNA double helix.
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PMID:Identity of the RNA-binding protein K of hnRNP particles with protein H16, a sequence-specific single strand DNA-binding protein. 752 36

The La (SS-B) autoimmune antigen is an RNA-binding protein that is present in both the nucleus and cytoplasm of eukaryotic cells, where it is found associated with RNA polymerase III transcripts. We have investigated the capacity of anti-La monoclonal antibodies SW1, SW3, and SW5 to immunoprecipitate human La ribonucleoprotein particles. Distinct differences were observed for SW3 in comparison with SW1 and SW5. While SW1 and SW5 precipitated ribonucleoproteins containing pre-tRNA, pre-5S rRNA, hY RNAs, pre-U6 snRNA or the viral EBER1 and VA RNAs, SW3 precipitated only ribonucleoproteins containing VA RNAs or (the precursor of) 7-2 RNA. Mapping of the epitopes recognized by SW1, SW3, and SW5 revealed that all three monoclonal antibodies recognize an epitope within the domain of the protein formed by the ribonucleoprotein motif. Cross-competition studies suggested that the epitope recognized by SW1 and SW5 are identical but distinct from the epitope recognized by SW3. Further analyses of the recognition of La from other species by these monoclonal antibodies revealed that they all reacted with bovine La and were not reactive with La from rodents and Xenopus laevis. Replacement of a single amino acid in the human protein by its murine counterpart abolished recognition by SW1 and SW5, but had no effect on recognition by SW3. Taken together, our results indicate that SW1 and SW5 recognize the same epitope and that SW3 recognizes a distinct epitope, both of which are located in the RNA-binding domain of La, and that the accessibility of these epitopes is differentially influenced by the association of La with various RNA polymerase III transcripts.
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PMID:Anti-La monoclonal antibodies recognizing epitopes within the RNA-binding domain of the La protein show differential capacities to immunoprecipitate RNA-associated La protein. 755 14

Many oncogenes associated with human sarcomas are composed of a fusion between transcription factors and the N-terminal portions of two similar RNA-binding proteins, TLS and EWS. Though the oncogenic fusion proteins lack the RNA-binding domain and do not bind RNA, the contribution from the N-terminal portion of the RNA-binding protein is essential for their transforming activity. TLS and EWS associate in vivo with RNA polymerase II (Pol II) transcripts. To learn more about the target gene specificity of this interaction, the localization of a Drosophila melanogaster protein that has extensive sequence identity to the C-terminal RNA-binding portions of TLS and EWS was studied in preparations of Drosophila polytene nuclei. cDNA clones encoding the full-length Drosophila TLS-EWS homolog, SARFH (stands for sarcoma-associated RNA-binding fly homolog), were isolated. Functional similarity to TLS and EWS was revealed by the association of SARFH with Pol II transcripts in mammalian cells and by the ability of SARFH to elicit homologous down-regulation of the levels of the mammalian proteins. The SARFH gene is expressed in the developing Drosophila embryo from the earliest stages of cellularization and is subsequently found in many cell types. In preparations of polytene chromosomes from salivary gland nuclei, SARFH antibodies recognize their target associated with the majority of active transcription units, revealed by colocalization with the phosphorylated form of RNA Pol II. We conclude that SARFH and, by homology, EWS and TLS participate in a function common to the expression of most genes transcribed by RNA Pol II.
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PMID:Association of SARFH (sarcoma-associated RNA-binding fly homolog) with regions of chromatin transcribed by RNA polymerase II. 762 47

Nearly 1 million interspersed Alu elements reside in the human genome. Alu retrotransposition is presumably mediated by full-length Alu transcripts synthesized by RNA polymerase III, while some polymerase III-synthesized Alu transcripts undergo 3'-processing and accumulate as small cytoplasmic (sc) RNAs of unknown function. Interspersed Alu sequences also reside in the untranslated regions of some mRNAs. The Alu sequence is related to a portion of the 7SL RNA component of signal recognition particle (SRP). This region of 7SL RNA together with 9- and 14-kDa polypeptides (SRP9/14) regulates translational elongation of ribosomes engaged by SRP. Here we characterize human (h) SRP9 and show that it, together with hSRP14 (SRP9/14), forms the activity previously identified as Alu RNA-binding protein (RBP). The primate-specific C-terminal tail of hSRP14 does not appreciably affect binding to scAlu RNA. Kd values for three Alu-homologous scRNAs were determined using Alu RBP (SRP9/14) purified from HeLa cells. The Alu region of 7SL, scAlu, and scB1 RNAs exhibited Kd values of 203 pM, 318 pM, and 1.8 nM, respectively. Finally, Alu RBP can bind with high affinity to synthetic mRNAs that contain interspersed Alus in their untranslated regions.
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PMID:Human signal recognition particle (SRP) Alu-associated protein also binds Alu interspersed repeat sequence RNAs. Characterization of human SRP9. 773 Mar 21

The trans-activation response element (TAR) at the 5' end of the human immunodeficiency virus type 1 (HIV-1) mRNAs forms a stable hairpin structure which is a target for binding of the virally encoded protein Tat, which activates viral gene expression, as well as several cellular factors. TAR is also inhibitory to translation. One of several host factors that binds to TAR RNA is the La autoantigen, an RNA-binding protein which functions in RNA polymerase III transcription termination and has also been implicated in cap-independent internal translation initiation on poliovirus RNA. Here we show that La autoantigen alleviates translational repression by the HIV-1 leader RNA. In rabbit reticulocyte lysate, La relieves the cis-inhibitory effect of the TAR RNA on translation of bacterial chloramphenicol acetyltransferase (CAT) mRNA but not inhibition that is mediated by an artificial secondary structure element. Canonical translation factors exhibited slight (eIF-2 and GEF) or no (eIF-4A, eIF-4B, eIF-4E, eIF-4F, eIF-3, and eEF-1 alpha) stimulatory activity on translation of TAR-containing CAT mRNA. In addition, we show that poliovirus RNA, in spite of being an inefficient template in rabbit reticulocyte lysate, is a strong competitive inhibitor of translation of TAR-containing CAT mRNA but not CAT mRNA. This inhibition can be relieved by La but not by any other translation factor. The results suggest a possible involvement of the La autoantigen in HIV-1 gene expression.
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PMID:La autoantigen alleviates translational repression by the 5' leader sequence of the human immunodeficiency virus type 1 mRNA. 793 82


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