Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.1 (S1 nuclease)
3,660 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Southern blot analysis of genomic DNA of the mesophilic lactic bacterium Lactococcus lactis subsp. lactis strain IL1403, illuminated six rRNA gene clusters. Each cluster contains one copy each of three rRNA genes, displaying the typical eubacterial organization of physically linked 16 S, 23 S and 5 S rRNA genes. Five of the six rRNA clusters were cloned into plasmid pBR322. One recombinant plasmid, pSLCM6, containing a 6500 base-pair genomic DNA fragment, was characterized by physical mapping and the sequences encoding rRNAs and tRNAs were localized by Southern hybridization. This fragment contains a single operon composed of one promoter, a leader sequence, a 16 S rRNA gene, a tRNA(Ala) gene, a 23 S rRNA gene, a 5 S rRNA gene and a tRNA(Asn) gene. S1 nuclease mapping and primer extension analysis of in vivo transcripts localized one transcriptional initiation site 150 base-pairs upstream from the start of the 16 S rRNA gene. These procedures also suggest that this transcript is processed by an RNAse III-like activity similar to Bacillus subtilis; i.e. the L. lactis nuclease might be sequence-specific. The chronology of specific cleavages occurring during the maturation process of the precursor transcript is described. One interesting observation is that the regions flanking the 16 S and 23 S rRNAs containing the primary processing sites are identical and contain sequences that could be involved in transcriptional antitermination. S1 mapping of the 3' ends of in vivo transcripts indicate that a terminator-like sequence a few base-pairs downstream from the distal tRNA(Asn) gene is inefficient in arresting transcription.
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PMID:Gene organization, primary structure and RNA processing analysis of a ribosomal RNA operon in Lactococcus lactis. 845 May 51

Selenocysteine-inserting tRNAs (or tRNA(Sec)) are structurally untypical tRNAs that are charged by seryl-tRNA synthetase before being recognized by the selenocysteine synthase that converts serine into selenocysteine. tRNA(Sec) from Escherichia coli contains 95 nucleotides and is the longest tRNA known to date, in contrast to canonical tRNA(Ser), 88 nucleotides-long. We have studied its solution conformation by chemical and enzymatic probing. Global structural features were obtained by cobra venom and S1 nuclease mapping, as well as by probing with Pb2+. Accessibilities of phosphate groups were measured by ethylnitrosourea probing. Information about positions in bases involved in Watson-Crick pairing, in stacking or in tertiary interactions were obtained by chemical probing with dimethylsulfate, diethylpyrocarbonate, kethoxal and carbodiimide. On the basis of these chemical data, a three-dimensional model was constructed by computer modeling and compared to that of canonical tRNA(Ser). tRNA(Sec) resembles tRNA(Ser) at the level of its T-arm and anticodon-arm conformations, as well as at the joining of the D- and T-loops by a tertiary Watson-Crick G19-C56 interaction. Its extra-long variable arm is a double-stranded structure closed by a four nucleotide loop that is linked to the body of the tRNA in a way different from that found in tRNA(Ser). As anticipated from the peculiar features of the sequence in the D-loop and at the junction of amino acid and D-arms, tRNA(Sec) possesses a novel but restricted set of tertiary interactions in the core of its three-dimensional structure: a G8-A21-U14 triple pair and a novel interaction between C16 of the D-loop and C59 of the T-loop. A third triple interaction involving C15-G20a-G48 is suggested but some experimental evidence for it is still lacking. It is furthermore concluded that the D-arm has six base-pairs instead of three, as in canonical class II tRNA(Ser), with the D-loop containing only four nucleotides. Finally, the amino acid accepting arm forms a stack of eight Watson-Crick base-pairs (instead of 7 in other tRNAs). The biological relevance of this model with regard to interaction with seryl-tRNA synthetase and enzymes from the selenocysteine metabolism is discussed.
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PMID:Solution structure of selenocysteine-inserting tRNA(Sec) from Escherichia coli. Comparison with canonical tRNA(Ser). 851 Jan 47

The three consecutive G:C base pairs, G29:C41, G30:C40, and G31:C39, are conserved in the anticodon stem of virtually all initiator tRNAs from eubacteria, eukaryotes, and archaebacteria. We show that these G:C base pairs are important for function of the tRNA in initiation of protein synthesis in vivo. We changed these base pairs individually and in combinations and analyzed the activities of the mutant Escherichia coli initiator tRNAs in initiation in vivo. For assessment of activity of the mutant tRNAs in vivo, mutations in the G:C base pairs were coupled to mutation in the anticodon sequence from CAU to CUA. Mutations in each of the G:C base pairs reduced activity of the mutant tRNA in initiation, with mutation in the second G:C base pair having the most severe effect. The greatly reduced activity of this C30:G40 mutant tRNA is not due to defects in aminoacylation or formulation of the tRNA or defects in base modification of the A37, next to the anticodon, which we had previously shown to be important for activity of the mutant tRNAs in initiation. The anticodon stem mutants are most likely affected specifically at the step of binding to the ribosomal P site. The pattern of cleavages in the anticodon loop of mutant tRNAs by S1 nuclease indicate that the G:C base pairs may be involved directly in interactions of the tRNA with components of the P site on the ribosome rather than indirectly by inducing a particular conformation of the anticodon loop critical for function of the tRNA in initiation.
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PMID:Role of the three consecutive G:C base pairs conserved in the anticodon stem of initiator tRNAs in initiation of protein synthesis in Escherichia coli. 866 14

Structural differences between native yeast tRNA(Phe), its in vitro transcript and the U8G mutant have been investigated using metal ion-induced hydrolysis and nuclease digestion. Differences in the solution structure of the molecules involve four regions: the D- and T-loops, the variable region and the anticodon loop. Efficiency of the Pb(II); Eu(II)-, Mn(II)- and Mg(II)-induced hydrolysis at the main cleavage sites in the D-loop is significantly reduced for unmodified tRNAs. Moreover, only the in vitro transcripts are susceptible for cleavage in the T-loop and entire anticodon loop. Other changes in the transcript molecule involve 50-fold enhancement of S1 nuclease digestion at p36, weak cleavages in the D-loop and lack of some digestion sites in the T-loop. The nuclease V1 digestion patterns are very similar for studied molecules. Changes in the pattern of hydrolysis of the D-loop caused by mutation of the conservative base U8 to G are detected by metal-induced hydrolysis only. Our results indicate clearly that metal ions and enzymatic probes monitor different features of RNA structure and their combined use is highly advantageous in studying subtle structural changes in tRNA.
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PMID:Effect of modified nucleotides on structure of yeast tRNA(Phe). Comparative studies by metal ion-induced hydrolysis and nuclease mapping. 881 22

We have studied the interactions between Escherichia coli tRNAVal and valyl-tRNA synthetase (ValRS) by enzymatic footprinting with nuclease S1 and ribonuclease V1, and by analysis of the aminoacylation kinetics of mutant tRNAVal transcripts. Valyl-tRNA synthetase specifically protects the anticodon loop, the 3' side of the stacked T-stem/acceptor-stem helix, and the 5' side of the anticodon stem of tRNAVal against cleavage by double- and single-strand-specific nucleases. Increased nuclease susceptibility at the ends of the anticodon- and T-stems in the tRNAVal.ValRS complex is indicative of enzyme-induced conformational changes in the tRNA. The most important synthetase recognition determinants are the middle and 3' anticodon nucleotides (A35 and C36, respectively); G20, in the variable pocket, and G45, in the tRNA central core, are minor recognition elements. The discriminator base, position 73, and the anticodon stem also are recognized by ValRS. Replacing wild-type A73 with G73 reduces the aminoacylation efficiency more than 40-fold. However, the C73 and U73 mutants remain good substrates for ValRS, suggesting that guanosine at position 73 acts as a negative determinant. The amino acid acceptor arm of tRNAVal contains no other synthetase recognition nucleotides, but regular A-type RNA helix geometry in the acceptor stem is essential [Liu, M., et al. (1997) Nucleic Acids Res. 25, 4883-4890]. In the anticodon stem, converting the U29:A41 base pair to C29:G41 reduces the aminoacylation efficiency 50-fold. This is apparently due to the rigidity of the anticodon stem caused by the presence of five consecutive C:G base pairs, since the A29:U41 mutant is readily aminoacylated. Identity switch experiments provide additional evidence for a role of the anticodon stem in synthetase recognition. The valine recognition determinants, A35, C36, A73, G20, G45, and a regular A-RNA acceptor helix are insufficient to transform E. coli tRNAPhe into an effective valine acceptor. Replacing the anticodon stem of tRNAPhe with that of tRNAVal, however, converts the tRNA into a good substrate for ValRS. These experiments confirm G45 as a minor ValRS recognition element.
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PMID:Synthetase recognition determinants of E. coli valine transfer RNA. 1038 13

A cluster of six genes, tRNA(Trp)-secE-nusG-rplK-rplA-pkwR, was cloned and sequenced from a Corynebacterium glutamicum cosmid library and shown to be contiguous in the C. glutamicum genome. These genes encode a tryptophanyl tRNA, the protein translocase component SecE, the antiterminator protein NusG, and the ribosomal proteins L11 and L1 in addition to PkwR, a putative regulatory protein of the LacI-GalR family. S1 nuclease mapping analysis revealed that nusG and rplK are expressed as separate transcriptional units and rplK and rplA are cotranscribed as a single mRNA. A 19-nucleotide inverted repeat that appears to correspond to a transcriptional terminator was located in the 3' region downstream from nusG. Northern analysis with different probes confirmed the S1 mapping results and showed that the secE-rplA four-gene region gives rise to four transcripts. secE was transcribed as a 0.5-kb monocistronic mRNA, nusG formed two transcripts of 1.4 and 1.0 kb from different initiation sites, and the two ribosomal protein genes rplK and rplA were cotranscribed as a single mRNA of 1.6 kb. A consensus L1 protein binding sequence was identified in the leader region of the rplK-rplA transcript, suggesting that expression of the rplK-rplA cluster was regulated by autogenous regulation exerted by the L1 protein at the translation level. The promoters of the nusG and rplK-rplA genes were subcloned in a novel corynebacterial promoter-probe vector and shown to confer strong expression of the reporter gene.
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PMID:Organization and transcriptional analysis of a six-gene cluster around the rplK-rplA operon of Corynebacterium glutamicum encoding the ribosomal proteins L11 and L1. 1131 98

Aminoacylation of tRNA was attempted through formation of tRNA/DNA/aa-PNA (N-aminoacylated peptide nucleic acid) ternary hybrid. A 23-mer DNA, that is complementary to a 3'-terminal of tRNA and to a 9-mer PNA carrying an amino acid unit, was designed to achieve close proximity between the amino acid and the 3'-OH group of tRNA. The aminoacylation was carried out in a buffer solution containing imidazole. The aminoacylation was detected by nuclease S1 treatment followed by HPLC and MALDI-TOF MS. This novel methodology will open a way for easy and versatile aminoacylation of nonnatural amino acids onto specific tRNAs.
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PMID:Aminoacylation of tRNA by antisense molecule. 1290 25

Most photosynthesis-related genes in mature chloroplasts are transcribed by a eubacterial-type RNA polymerase (PEP) whose core subunits are encoded by the plastid genome. It has been shown previously that six putative nuclear genes (SIG1 to SIG6) encode promoter-specificity factors for PEP in Arabidopsis thaliana, and we isolated a T-DNA insertion line of SIG2 (sig2-1 mutant) that manifests aberrant chloroplast development. With the use of S1 nuclease protection and primer extension analyses, we have now characterized the SIG2-dependent chloroplast promoters in A.thaliana. The amounts of transcripts derived from one of the multiple psbD promoters (psbD -256) and from the promoters of two tRNA genes (trnE-UUC and trnV-UAC) were markedly and specifically decreased in the sig2-1 mutant. The abundance of these transcripts was restored to wild-type levels by introduction into the mutant of a SIG2 transgene. The recombinant SIG2 protein mixed with Escherichia coli core RNA polymerase could bind to a DNA fragment that contains the SIG2-dependent psbD -256, trnE-UUC or trnV-UAC promoter. Sequences similar to those of the -35 and -10 promoter elements of E.coli were identified in the regions of the SIG2-dependent chloroplast genes upstream of the transcription initiation sites.
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PMID:Molecular genetic analysis of chloroplast gene promoters dependent on SIG2, a nucleus-encoded sigma factor for the plastid-encoded RNA polymerase, in Arabidopsis thaliana. 1465 84

To investigate gene organization and expression signals in extreme thermophilic archaebacteria, tRNA genes were cloned from Thermoproteus tenax. Clones for five tRNA species were obtained, namely for tRNAAla (TGC), tRNAAla (CGC), tRNALeu (CAG), tRNALeu (CAA) and tRNAMet (CAT). Three of the respective genes were located singly in the chromosome, the two others (tRNAAla and tRNAMet) were clustered but in a head to head position. Four of the genes contained intervening sequences, either in the classical position 3' to the anticodon (tRNAMet), or within the anticodon sequence (tRNALeuCAG), or in the hitherto unique position 5' to the anticodon within the anticodon stem region (tRNAAla). Existence of a transcript containing the intervening sequence was demonstrated by nuclease S1 mapping. All tRNA genes were extremely rich in G-C basepairs of helical regions, a feature which may contribute to thermostability of the secondary structure. The start site of transcription of the 16S/23S rRNA operon and of two tRNA genes of Thermoproteus was determined by nuclease S1 mapping. Transcription of the tRNA genes initiates close to or immediately at the 5' end of the structural gene, that of the rRNA operon 175 bp upstream of the coding region. About 18 bp upstream of the transcription initiation site a conserved AT-rich sequence motif occurs within a fairly GC-rich intercistronic spacer. Its putative instability at the high growth temperature of Thermoproteus suggests a function as entry site for RNA polymerase.
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PMID:Genes for stable RNA in the extreme thermophile Thermoproteus tenax: introns and transcription signals. 1598 38

We analyzed expression elements of three disparate groups of mitochondrial genes in Neurospora crassa, apocytochrome b (COB), cytochrome c oxidase 1 (COX1), and the clustered ATP8-ATP6-mtATP9-COX2. To identify promoter sequences we employed the published N. crassa consensus sequence for COB and rRNA genes, and we found closely related sequences within the 5'-regions of both COX1 and the ATP8-COX2 transcriptional units. We determined that the mature COX1 RNA includes two flanking unassigned reading frame (URF) sequences, but the 3'-flanking ND1 is not included in the COX1 mRNA. The ATP8-ATP6-mtATP9-COX2 polycistronic transcript does not include an adjacent 5'-URF sequence. Primer extension analysis showed one likely 5'-end for the COX1 transcript, which is 73 nucleotides downstream of the consensus promoter sequence and is the first nucleotide 3' of the sequence for the tRNA(cys). Primer extension analysis and S1 nuclease mapping of the ATP8-COX2 RNA showed that the 5'-end for this transcript is the first nucleotide 3' of the consensus promoter sequence. We performed gel-shift experiments to detect proteins in mitochondria that bind to transcripts as possible regulatory proteins. The 5'-untranslated region (UTR) RNAs of COB, COX1, and ATP8-COX2 appear to bind both unique proteins and an overlapping group of two to four proteins of approximately 155-45 M(r). We successively deleted regions of the RNA 5'-UTRs to identify sequences that bound these proteins. Similar predicted stem-loop secondary structures were detected in the protein-binding regions of all three UTRs.
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PMID:Transcripts and transcript-binding proteins in mitochondria of Neurospora crassa. 1612 Mar 32


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