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Transcription and replication of the influenza virus RNA genome take place in the nuclei of infected cells. Ribonucleoprotein (RNP) complexes consisting of viral RNA, RNA polymerase, and nucleocapsid protein (NP) are proven to be the catalytic unit for RNA synthesis, while it has been indicated that the viral RNA polymerase activity is modulated by host-derived nuclear factors. Here we have identified...
Genetic evidence in yeast has revealed that a non-Watson-Crick base-pairing interaction between terminal guanosine residues of the intron is required for the second step of pre-mRNA splicing. To explore the likely configuration of the interaction between the terminal guanosines of the intron, inosine was uniformly incorporated into an adenovirus pre-mRNA substrate (Ade) to replace guanosine residues...
Mammalian cells contain suppressor tRNAs that can translate nonsense codons such as UAG and UGA localized at a specific site of natural mRNAs. For translation of these nonsense codons, a specific secondary or tertiary structure of mRNAs located in the region surrounding the translatable nonsense codon is required. In mammalian cells, transcriptional expression of the tRNA gene encoding UAG suppressor...
10Sa RNA is a small stable bacterial RNA in which the 5 - and 3 -end sequences are folded into a tRNA-like structure. The RNA is aminoacylatable with alanine in vitro, and it interacts with 70S ribosomes in the cell. Recently, Escherichia coli 10Sa RNA has been shown to contain the sequence-encoding tag-peptides, which are found to attach to the C-termini of truncated peptides synthesized in vivo...
A number of Candida species translate the standard leucine CUG codon as serine rather than as leucine. Such codon reassignment in nuclear-encoded mRNAs is unusual and raises a number of important questions about the origin of the genetic code and its continuing evolution. In particular we must establish how a codon can come to be reassigned without extinction of the species and what, if any, selective...
The hallmark features of rho-independent transcription terminators are a G+C-rich dyad symmetry sequence followed by a run of T residues on a sense strand. Both of these structural elements are required for efficient transcription termination. Besides its primary function, rho-independent terminators are also known to enhance expression of an upstream gene by stabilizing RNA in a few cases. The...
Nonsense codons between position 14 within the first exon and position 193 within the penultimate exon of the human gene for triosephosphate isomerase reduce mRNA abundance to 25% of normal. The reduction in abundance is due to the decay of newly synthesized mRNA that copurifies with nuclei. TPI mRNA that copurifies with cytoplasm is immune to decay. We show here that immunity is not due to the...
Human immunodeficiency virus type-1 (HIV-1) Rev acts by inducing the specific nucleocytoplasmic transport of a class of incompletely spliced RNAs that encodes the viral structural proteins. The transfection of HeLa cells with a rev-defective HIV-1 expression plasmid, however, resulted in the export of overexpressed, intron-containing species of viral RNAs, possibly through a default process of nuclear...
A model is presented for the regulation of the double-stranded RNA (dsRNA)-activated mammalian protein kinase PKR, which is involved in protein synthesis inhibition and the antiviral response in cells. A series of previous findings abut PKROs behavior are reviewed, including its effects on translation; the activation of its protein kinase activity; binding sites for PKR on RNA; PKROs protein domains,...
The last two amino acids of the nascent peptide at the ribosomal P-site influence the efficiency of termination readthrough at the stop codon UGA (Mottagui-Tabar et al (1994) EMBO J 13, 249-257; Bjornsson et al (1996) EMBO J 15, 1696-1704). Here we analyze this effect on readthrough by wild type or a UGA suppressor form (Su9) of tRNA Trp by varying the codons at positions -1 and...
The gene encoding the ribosomal protein from Thermus thermophilus, TL5, which binds to the 5S rRNA, has been cloned and sequenced. The codon usage shows a clear preference for G/C rich codons that is characteristic for many genes in thermophilic bacteria. The deduced amino acid sequence consists of 206 residues. The sequence of TL5 shows a strong similarity to a general shock protein from Bacillus...
A variety of transcription attenuation mechanisms are used by bacteria to regulate gene and operon expression. This review summarizes previous and current studies designed to elucidate the features of the specific attenuation mechanisms that regulate expression of the tryptophanase (tna) operon of Escherichia coli and the tryptophan (trp) operon of Bacillus subtilis. Initiation of transcription...
Wide ranging studies of the readthrough of translational stop codons within the last 25 years have suggested that the stop codon might be only part of the molecular signature for recognition of the termination signal. Such studies do not distinguish between effects on suppression and effects on termination, and so we have used a number of different approaches to deduce whether the stop signal is...
Cytoplasmic tRNA Asp of rat liver was purified by the solid-phase hybridization method and its nucleotide sequence was analyzed by Donis-Keller's method. The results suggested that the two nucleotides next to the anticodon were identical to its gene sequence, a finding that is inconsistent with a previous report demonstrating by several methods that C32 and T33 on the tRNA A...
The refined crystal structure of the ternary complex of yeast Phe-tRNA Phe , Thermus aquaticus elongation factor EF-Tu and the non-hydrolyzable GTP analog, GDPNP, reveals many details of the EF-Tu recognition of aminoacylated tRNA (aa-tRNA). EF-Tu-GTP recognizes the aminoacyl bond and one side of the backbone fold of the acceptor helix and has a high affinity for all ordinary elongator...
In order to design the best construct for therapeutic hammerhead ribozymes against AML1-MTG8, the t(8;21)-associated fusion mRNA of acute myeloid leukemia, we synthesized DNA/RNA chimeric ribozymes directed to the area adjacent to the fusion point between AML1 and MTG8. Catalytic efficiency and fusion gene specificity of ribozymes were examined by kinetic studies of the cleavage reactions of AML1-MTG8,...
The Escherichia coli rnc-era-recO operon encodes ribonuclease III (RNase III; a dsRNA endonuclease involved in rRNA and mRNA processing and decay), Era (an essential G-protein of unknown function) and RecO (involved in the RecF homologous recombination pathway). Expression of the rnc and era genes is negatively autoregulated: RNase III cleaves the rncO operator in the untranslated leader, destabilizing...
We summarize in this communication the data supporting the two functions of ribosome recycling factor (RRF, originally called ribosome releasing factor). The first described role involves the disassembly of the termination complex which consists of mRNA, tRNA and the ribosome bound to the mRNA at the termination codon. This process is catalyzed by two factors, elongation factor G (EF-G) and RRF...
A structural model was established for the N-terminal part of translation factor SelB which shares sequence similarity with EF-Tu, taking into account the coordinates of the EF-Tu 3D structure and the consensus of SelB sequences from four bacteria. The model showed that SelB is homologous in its N-terminal domains over all three domains of EF-Tu. The guanine nucleotide binding site and the residues...
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