[The role of bacteriophage lambda coded proteins in destruction of the bacterial cell wall and the control of lysis timing].
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Previous work has established that the E. coli htrA gene product is essential for bacterial survival at temperatures above 42 degrees. We have sequenced the htrA gene region and found an open reading frame (ORF) coding for a protein of 491 amino acids with a calculated molecular weight of 51,163 daltons. This molecular weight corresponds well with that seen following electrophoresis on SDS-polyacrylamide gels. This protein has an amino-terminal sequence typical for a leader peptide and undergoes post-translational modification by cleavage of an amino-terminal portion. The insertional mutations which affect the function of the htrA gene map inside this ORF. The levels of htrA mRNA increase rapidly and transiently upon heat shock in a manner independent of the rpoH gene, which encodes the sigma 32 RNA polymerase subunit and is known to regulate transcription of typical heat shock genes. Using S1 mapping and RNA primer extension, we have identified the htrA promoter and found that it is similar to the P3 promoter of the rpoH gene. The P3 promoter is especially active at high temperatures and is recognized by a recently identified transcriptional factor, sigma E.
The protein coding region of the herpes simplex virus type-1 glycoprotein D (gD) gene was mapped, and the nucleotide sequence was determined. The predicted amino acid sequence of the gD polypeptide was found to contain a number of features in common with other virus glycoproteins. Insertion of this protein coding region into a bacterial expressor plasmid enabled synthesis in Escherichia coli of an immunoreactive gD-related polypeptide. The potential of this system for preparation of a type-common herpes simplex virus vaccine is discussed.
Recombinant plasmids in which the sequence encoding the bacterial chloramphenicol acetyltransferase (CAT; acetyl-CoA:chloramphenicol 3-O-acetyltransferase, EC 2.3.1.28) has been placed under the control of Drosophila heat shock protein 70 (hsp 70) or copia promoters have been introduced into cultured cells of two Drosophila species (Schneider II line of Drosophila melanogaster and D. immigrans) as calcium-phosphate complexes. Within 1-2 days after transfection functional CAT enzyme was detected in cells exposed to either CAT recombinant. The expression of the bacterial information depends on the activity of the Drosophila promoters because plasmids in which the Drosophila DNA fragments were fused to the CAT coding sequence in inverted orientation did not support the synthesis of CAT enzyme activity. Low levels of CAT activity and of hybrid mRNA were detected in cells transformed with hsp-cat recombinants when the cells were maintained at room temperature, and both mRNA levels and CAT activity increased substantially after a brief exposure to 37 degrees C. hsp-cat mRNA has the same 5' terminus as authentic Drosophila hsp 70 messenger. These experiments document a practical system for the introduction and expression of isolated genes in cultured cells of Drosophila.
The transcription and translation of the tellurite-resistance (TeR) genes of the HII incompatibility group plasmid, pHH1508a, were studied. The nucleotide (nt) sequence of the TeR region was determined and two possible open reading frames, tehA and tehB, were identified. The direction of transcription and translation of these genes was confirmed through the preparation of lacZ and phoA (encoding alkaline phosphatase) fusions. The transcription start point was identified in the sequence using RNA primer extension. The tehA gene codes for a 36-kDa polypeptide which is highly hydrophobic. The TehA protein appears to be located in the inner membrane of the bacterial cell since tehA fusions with both phoA and lacZ were obtained and expressed. The tehB gene codes for a 23-kDa polypeptide which appears to be relatively hydrophilic and is probably located in the cytoplasm. Both proteins were overproduced using a T7 RNA polymerase/promoter system. No nt or amino acid sequence homology could be found between this TeR determinant and the TeR genes from the IncHI-2 plasmid, pMER610, and the IncP alpha plasmid, RK2.
BACKGROUND: Transcription slippage occurs on certain patterns of repeat mononucleotides, resulting in synthesis of a heterogeneous population of mRNAs. Individual mRNA molecules within this population differ in the number of nucleotides they contain that are not specified by the template. When transcriptional slippage occurs in a coding sequence, translation of the resulting mRNAs yields more than one protein product. Except where the products of the resulting mRNAs have distinct functions, transcription slippage occurring in a coding region is expected to be disadvantageous. This probably leads to selection against most slippage-prone sequences in coding regions. RESULTS: To find a length at which such selection is evident, we analyzed the distribution of repetitive runs of A and T of different lengths in 108 bacterial genomes. This length varies significantly among different bacteria, but in a large proportion of available genomes corresponds to nine nucleotides. Comparative sequence analysis of these genomes was used to identify occurrences of 9A and 9T transcriptional slippage-prone sequences used for gene expression. CONCLUSIONS: IS element genes are the largest group found to exploit this phenomenon. A number of genes with disrupted open reading frames (ORFs) have slippage-prone sequences at which transcriptional slippage would result in uninterrupted ORF restoration at the mRNA level. The ability of such genes to encode functional full-length protein products brings into question their annotation as pseudogenes and in these cases is pertinent to the significance of the term 'authentic frameshift' frequently assigned to such genes.
Knockout (KO) mice lacking steroidogenic factor 1 (SF-1, officially designated Nr5a1) have a complex phenotype that includes adrenal and gonadal agenesis, impaired function of pituitary gonadotropes, and abnormalities of the ventromedial hypothalamic nucleus (VMH). To develop a lineage marker for cells that express SF-1, we used bacterial artificial chromosome (BAC) transgenesis. A BAC fragment containing 50 kb of the mouse Nr5a1 gene was placed upstream of the coding sequence for enhanced green fluorescent protein (eGFP) and used to generate SF-1/eGFP transgenic mice. These sequences directed eGFP expression to multiple cell lineages that express SF-1, including steroidogenic cells of the adrenal cortex, testes, and ovaries, VMH neurons, and reticuloendothelial cells of the spleen. Despite the essential role of SF-1 in gonadotropes, eGFP was not expressed in the anterior pituitary. These studies show that 50 kb of the mouse Nr5a1 gene can target transgenic expression to multiple cell lineages that normally express SF-1. The SF-1/eGFP transgene provides a valuable tool to expand our understanding of the actions of SF-1 in endocrine development and function.
The GUT1 gene of Saccharomyces cerevisiae, encoding glycerol kinase, was cloned and sequenced. The cloned genomic DNA fragment contains an open reading frame potentially coding for a protein of 709 amino acids with homology to bacterial glycerol kinases (40.8% identity over 502 amino acids, and 42.1% identity over 496 amino acids, in comparison to the smaller E. coli and B. subtilis enzymes). Disruption of GUT1 showed that the gene is required for growth on glycerol, but not on glucose or ethanol media. No glycerol kinase activity was detected in the disruption mutant. According to enzyme activity and transcript analysis, synthesis of glycerol kinase is repressed by glucose, and derepression is ADR1-dependent.
The nucleotide sequence of the frdA gene, which encodes the flavoprotein subunit of the fumarate reductase, of Escherichia coli, has been determined. A polypeptide of Mr = 66,052, containing 602 amino acid residues, is predicted. In composition the FrdA protein strongly resembles the flavoprotein subunits of two succinate dehydrogenases. Moreover, a sequence of nine consecutive residues is common to the flavoprotein subunits from fumarate reductase and the beef heart succinate dehydrogenase. This sequence contains a histidyl residue which probably services as the site for attachment of the FAD cofactor to the reductase.
A 1194 bp open reading frame that codes for a 398 amino acid peptide was cloned from a lambda gt11 library of Drosophila melanogaster genomic DNA. The predicted peptide sequence is very similar to three previously characterized protein sequences that are encoded by the ftsZ genes in Escherichia coli, Bacillus subtilis and Rhizobium meliloti. The FtsZ protein has a major role in the initiation of cell division in prokaryotic cells. Using a tetracycline treatment that eradicates bacterial parasites from insects, the ftsZ homologue has been found to be derived from a bacterium that lives within the D. melanogaster strain. However, polymerase chain reaction (PCR) amplification of the gene from treated embryos suggests that it is not derived from a gut bacterium. Nevertheless, by amplifying and characterizing part of the 16S rRNA from this bacterium we have been able to demonstrate that it is a member of the genus Wolbachia, a parasitic organism that infects, and disturbs the sexual cycle of various strains of Drosophila simulans. We suggest that this ftsZ homologue is implicated in the cell division of Wolbachia, an organism that fails to grow outside the host organism. Sequence and alignment analysis of this ftsZ homologue show the presence of a potential GTP-binding motif indicating that it may function as a GTPase. The consequences of this function particularly with respect to its role in cell division are discussed.
The Chlorella virus IL-3A gene encoding the DNA methyltransferase M.CviJI, which methylates the internal cytosine in (G/A)GC(T/C/G) sequences, was cloned and expressed in Escherichia coli. The region containing the M.CviJI gene was sequenced and a single open reading frame of 1101 bp was identified that could code for a polypeptide of 367 amino acids with a predicted molecular weight of 41,864. M.CviJI contained regions of amino acids which were similar to bacterial cytosine methyltransferases. Eighteen other Chlorella viruses, of 36 tested, contained DNA sequences which hybridized to the M.CviJI gene; DNA from some, but not all, of these 18 viruses also contained 5-methylcytosine in (G/A)GC(T/C/G) sequences.
Integration of bacteriophage P2 into the Escherichia coli host genome involves recombination between two specific attachment sites, attP and attB, one on the phage and the other on the host genome, respectively. The reaction is controlled by the product of the phage int gene, a basic polypeptide of about 37 kDa [Ljungquist and Bertani, Mol. Gen. Genet. 192 (1983) 87-94]. The int gene appears to be expressed differently by an infecting phage, as opposed to a prophage [Bertani, Proc. Natl. Acad. Sci. USA 65 (1970) 331-336]. A 1200-bp region of P2 DNA containing the int gene and attP, the prophage hybrid ends attL and attR, and one bacterial attachment site, the preferred site locI from E. coli strain C, have all been sequenced. An open reading frame coding for a polypeptide of 337 amino acids corresponds to the int gene. The gene has no obvious promoter sequence preceding it. The int gene transcript seems to continue past the attP site downstream from it, suggesting a possible explanation for the previously observed difference in integration and excision. A comparison of the four attachment sites reveals a common 'core' sequence of 27 bp: 5'-AAAAAATAAGCCCGTGTAAGGGAGATT-3'. The P2 nip1 mutation, which increases prophage excision [Calendar et al., Virology 47 (1972) 68-75], was found to lie within the int gene itself. The P2 saf variant, which has altered site preference [Six, Virology 29 (1966) 106-125], has a bp substitution within the core sequence. Three deletion/substitution mutants, vir22, vir94 and del3, also have altered core sequences.
Transgenic mouse lines were engineered to express stably antisense mRNA or antisense mRNA containing catalytic ribozyme (rbz) structures complementary to bacterial chloramphenicol acetyltransferase (CAT) gene transcripts. One transgenic line expressed antisense mRNA that specifically targeted full-length CAT coding sequences (ACAT). Another transgenic line expressed full-length antisense CAT mRNA which was modified by mutagensis to include four rbz cassettes (rbz-ACAT) in order to compare antisense versus antisense-rbz function in vivo. Preliminary data were also collected from a transgenic mouse line expressing antisense mRNA targeting 72% of the 5' region of CAT coding sequences (5' ACAT). All constructs contained similar control elements in their design. Promoter elements were derived from the bovine alpha s1-casein gene, while the small t intron and 3' control sequences were derived from SV40. The ability of these various constructs to down-regulate CAT protein levels was compared by analysis of CAT protein production in lactating double-hemizygous transgenic female mice. Every double-hemizygous mouse analysed expressed mRNA from the alpha s1-casein-CAT construct (Clarke et al., 1994) and equivalent levels of mRNA from one of the three antisense constructs. Transgenic mouse lines expressing both ACAT and CAT mRNA down-regulated CAT protein levels by 90% of that found in the CAT only transgenic population. Similarly, double-hemizygous transgenic lines expressing both rbz-ACAT and CAT mRNA regulated CAT protein levels by 87%. Preliminary data suggests that expression of mRNA from 5' ACAT/CAT double-hemizygote mice allowed approximately 67% down-regulation of normal CAT protein levels. We conclude that incorporation of multiple ribozymes within the full-length antisense CAT construct does not enhance the effectiveness of antisense mRNA in the down-regulation of CAT protein production in our system.
We have generated transgenic mice that express a diverse repertoire of human sequence immunoglobulins. The expression of this repertoire is directed by light and heavy chain minilocus transgenes comprised of human protein coding sequences in an unrearranged, germ-line configuration. In this paper we describe the construction of these miniloci and the composition of the CDR3 repertoire generated by the transgenic mice. The largest transgene discussed is a heavy chain minilocus that includes human mu and gamma 1 coding sequences together with their respective switch regions. It consists of a single 61 kb DNA fragment propagated in a bacterial plasmid vector. Both human heavy chain classes are expressed in animals that carry the transgene. In light chain transgenic animals the unrearranged minilocus sequences recombine to form VJ joints that use all five human J kappa segments, resulting in a diversity of human-like CDR3 regions. Similarly, in heavy chain transgenics the inserted sequences undergo VDJ joining complete with N region addition to generate a human-like VH CDR3 repertoire. All six human JH segments and at least eight of the ten transgene encoded human D segments are expressed. The transgenic animals described in this paper represent a potential source of human sequence antibodies for in vivo therapeutic applications.
In this report we describe the rescue of a transfectant influenza A virus which stably expresses a heterologous protein, bacterial chloramphenicol acetyltransferase (CAT). The foreign sequences encoding CAT are expressed as part of an essential influenza virus segment, that coding for the neuraminidase (NA) protein. The novel way by which this was achieved involved inserting in frame the 16-amino-acid self-cleaving 2A protease of foot-and-mouth disease virus between the CAT and the NA coding sequences. The resultant gene produces a polyprotein which is proteolytically cleaved to release both CAT and NA. The intramolecular cleavage occurs at the C terminus of the 2A sequence between a glycine-proline dipeptide motif such that the released NA protein has an additional N-terminal proline residue. The transfectant virus is stable upon passage in tissue culture. CAT activity is expressed at high levels in cell culture supernatants and in the allantoic fluid of infected eggs. Since the chimeric segment must maintain the heterologous reading frame to retain viability, the virus stability is dependent upon concomitant synthesis of the heterologous protein. This design may be particularly appropriate for utilization of influenza virus as a mammalian expression vector.
A new bacterial species belonging to the genus Pseudoalteromonas is described on the basis of phenotypic characterization, and sequence analysis of its 16S rRNA-coding and gyrase B (gyrB) genes. Ten strains, isolated from sea water of Yamato Island, Sea of Japan, were Gram-negative, yellow, motile, polarly flagellated, aerobic, rod-shaped eubacteria and had a G + C content of 42 mol%. Analysis of the 16S rDNA sequence revealed a clear affiliation between these strains and members of the gamma-Proteobacteria. High similarity values were found with members of the genus Pseudoalteromonas and this was supported by fatty acid profiles. The 16S rDNA sequence similarity between strain F12-50-A1T and Pseudoalteromonas piscicida was very high (99.1%). However, molecular characterizations employing small subunit 16S rDNA sequences were at the limits of resolution for the differentiation of species in this genus. As a result, DNA-DNA hybridization and sequence analyses of a more rapidly evolving gyrB gene were performed. Our assertion that this strain represents a distinct bacterial species within the genus Pseudoalteromonas was supported by both of these molecular analyses. Species-specific PCR probes were designed for the gyrB gene and used for the rapid screening of F12-50-A1T-like strains, thereby confirming the species. As these strains cleave complex protein compounds of the Mytilus edulis foot by secreting proteases, the name Pseudoalteromonas peptidolytica sp. nov. is proposed, with strain F12-50-A1T (= MBICC F1250A1T) as the type strain.
The genetic code is based on aminoacylation reactions where specific amino acids are attached to tRNAs bearing anticodon trinucleotides. However, the anticodon-independent specific aminoacylation of RNA minihelix substrates by bacterial and yeast tRNA synthetases suggested an operational RNA code for amino acids whereby specific RNA sequences/structures in tRNA acceptor stems correspond to specific amino acids. Because of the possible significance of the operational RNA code for the development of the genetic code, we investigated aminoacylation of synthetic RNA minihelices with a human enzyme to understand the sequences needed for that aminoacylation compared with those needed for a microbial system. We show here that the species-specific aminoacylation of glycine tRNAs is recapitulated by a species-specific aminoacylation of minihelices. Although the mammalian and Escherichia coli minihelices differ at 6 of 12 base pairs, two of the three nucleotides essential for aminoacylation by the E. coli enzyme are conserved in the mammalian minihelix. The two conserved nucleotides were shown to be also important for aminoacylation of the mammalian minihelix by the human enzyme. A simple interchange of the differing nucleotide enabled the human enzyme to now charge the bacterial substrate and not the mammalian minihelix. Conversely, this interchange made the bacterial enzyme specific for the mammalian substrate. Thus, the positional locations (if not the actual nucleotides) for the operational RNA code for glycine appear conserved from bacteria to mammals.
The nucleotide sequence of the glg C gene of Escherichia coli K12, coding for ADP-glucose synthetase, has been determined. The structural gene consists of 1293 base pairs, which specify a protein of 431 amino acids. The amino acid sequence deduced from the DNA sequence is consistent with the known NH2-terminal amino acid sequence and the amino acid composition of ADP-glucose synthetase. The translation start of the structural gene of glycogen synthase, glg A, starts immediately after termination of the glg C gene.