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A dnaK homolog in the archaebacterium Methanosarcina mazei S6.

A fragment of genomic DNA cloned from the methanogenic archaebacterium, Methanosarcina mazei strain S6, was found to contain an 1857-bp open reading frame (ORF). A sequence matching the consensus ribosome-binding sequence determined for other methanogens was found upstream from the ORF. The amino acid (aa) sequence encoded by the ORF was compared with reference sequences and was found to be related to six DnaK sequences determined for five species of eubacteria (none exist for archaebacteria). The M. mazei S6 aa sequence was over 61% identical and over 77% similar (identities plus conservative substitutions) to the closest four reference sequences, which were all DnaKs. The gene described here is therefore proposed to be the first member of the dnaK family sequenced from the archaebacterial kingdom (Archaea). This finding confirms that DnaK proteins are highly conserved, occurring not only in eubacteria (Bacteria) and eukaryotes (Eucaria), but also in archaebacteria (Archaea).

Amino Acid Sequence↗

Leader-encoded open reading frames modulate both the absolute and relative rates of synthesis of the virion proteins of simian virus 40.

Numerous viral and cellular RNAs are polycistronic, including several of the late mRNA species encoded by simian virus 40 (SV40). The functionally bicistronic major late 16S and functionally tricistronic major late 19S mRNA species of SV40 contain the leader-encoded open reading frames (ORFs) LP1, located upstream of the sequence encoding the virion protein VP1, and LP1*, located upstream of the sequence encoding the virion proteins VP2 and VP3. To determine how these leader ORFs affect synthesis of the virion proteins, monkey cells were transfected with viral mutants in which either the leader-encoded translation initiation signal was mutated or the length and overlap of the leader ORF relative to the ORFs encoding the virion proteins were altered. The levels of initiation at and leaky scanning past each initiation signal were determined directly by quantitative analysis of the viral proteins synthesized in cells transfected with these mutants. Novel findings from these experiments included the following. (i) At least one-third of ribosomes bypass the leader-encoded translation initiation signal, GCCAUGG, on the SV40 major late 16S mRNA. (ii) At least 20% of ribosomes bypass even the consensus translation initiation signal, ACCAUGG, when it is situated 10 bases from the 5' end on the major late 16S mRNA. (iii)O The presence of the leader ORF on the bicistronic 16S mRNA species reduces VP1 synthesis threefold relative to synthesis from a similar RNA that lacks it. (iv) At least half and possibly all VP1 synthesized from the bicistronic 16S mRNA species is made by a leaky scanning mechanism. (v) LP1 and VP1 are synthesized from the bicistronic 16S mRNA species at approximately equal molar ratios. (vi) Approximately half of the VP1 synthesized in SV40-infected cells is synthesized from the minor, monocistronic 16S mRNA even though it accounts for only 20% of the 16S mRNA present. (vii) The presence and site of termination of translation of the leader ORF on the late 19S mRNAs affect the relative as well as absolute rates of synthesis of VP2 and VP3.

Genes, Viral↗

Cloning, sequencing and bacterial expression of human glycine tRNA synthetase.

The human glycine tRNA synthetase gene (GlyRS) has been cloned and sequenced. The 2462 bp cDNA for this gene contains a large open reading frame (ORF) encoding 685 amino acids with predicted M(r) = 77,507 Da. The protein sequence has approximately 60% identity with B. mori GlyRS and 45% identity with S. cerevisiae GlyRS and contains motifs 2 and 3 characteristic of Class II tRNA synthetases. A second ORF encoding 47 amino acids is found upstream of the large ORF. Translation of this ORF may precede the expression of GlyRS as a possible regulatory mechanism. The enzyme was expressed in E. coli as a fusion protein with a 13 kDa biotinylated tag with an apparent M(r) = 90 kDa. The fusion protein was immunoprecipitated from crude bacterial extract with human EJ serum, which contains autoantibodies directed against GlyRS, and with rabbit polyclonal serum raised against a synthetic peptide derived from the predicted amino acid sequence of human GlyRS. Bacterial extract containing the fusion protein catalyses the aminoacylation of bovine tRNA with [14C]-gly at 10-fold increased level above normal bacterial extract and confirms that the cDNA encodes human GlyRS.

Acylation↗

Diverse organization of genes of the beta-ketoadipate pathway in members of the marine Roseobacter lineage.

Members of the Roseobacter lineage, an ecologically important marine clade within the class alpha-Proteobacteria, harbor genes for the protocatechuate branch of the beta-ketoadipate pathway, a major catabolic route for lignin-related aromatic compounds. The genes of this pathway are typically clustered, although gene order varies among organisms. Here we characterize genes linked to pcaH and -G, which encode protocatechuate 3,4-dioxygenase, in eight closely related members of the Roseobacter lineage (pairwise 16S rRNA gene sequence identities, 92 to 99%). Sequence analysis of genomic fragments revealed five unique pca gene arrangements. Identical gene organization was found for isolates demonstrating species-level identity (i.e., >99% 16S rRNA gene similarity). In one isolate, six functionally related genes were clustered: pcaQ, pobA, pcaD, pcaC, pcaH, and pcaG. The remaining seven isolates lacked at least one of these genes in their clusters, although the relative order of the remaining genes was preserved. Three genes (pcaC, -H, and -G) were physically linked in all isolates. A highly conserved open reading frame (ORF) was found immediately downstream of pcaG in all eight isolates. Reverse transcription-PCR analysis of RNA from one isolate, Silicibacter pomeroyi DSS-3, provides evidence that this ORF is coexpressed with upstream pca genes. The absence of this ORF in similar bacterial pca gene clusters from diverse microbes suggests a niche-specific role for its protein product in Roseobacter group members. Collectively, these comparisons of bacterial pca gene organization illuminate a complex evolutionary history and underscore the widespread ecological importance of the encoded beta-ketoadipate pathway.

Adipates↗

The herpesvirus saimiri ORF 73 regulatory region provides long-term transgene expression in human carcinoma cell lines.

Herpesvirus saimiri (HVS) is capable of establishing a persistent infection in a variety of human carcinoma cell lines, by virtue of episomal maintenance. Moreover, the viral episome provides expression of a transgene in both in vitro and in vivo environments. At present, HVS vectors utilize heterologous promoters such as the IE hCMV promoter. However, this promoter maybe unsuitable for long-term expression in vivo, as promoter silencing has been observed in this and other herpesvirus-based vector systems. Ideal regulatory regions would be functional when the herpesvirus genome is maintained as a latent episome. We have previously shown that gene expression in an HVS-persistently-infected human carcinoma cell line is limited to an adjacent set of genes encoding ORFs 71-73. These genes are transcribed as a polycistronic mRNA species from a common regulatory region upstream of the ORF 73 gene. In this report, we assess the potential of the ORF 73 regulatory region to provide heterologous gene expression in a wide variety of human cancer cell lines. We demonstrate, utilizing transient transfection assays, that the ORF 73 regulatory region can provide transgene expression in a variety of human carcinoma cell lines, although levels of transgene expression are not as high as achieved under the control of heterologous promoters such as the IE hCMV promoter. Furthermore, incorporation of the minimal ORF 73 regulatory region in a recombinant HVS-based vector provides sustained expression of the green fluorescent protein in both in vitro and in vivo environments. These results suggest that the ORF 73 regulatory region may be suitable for use in HVS-based cancer gene therapy applications.

Adenocarcinoma↗

A pathogenicity gene isolated from the pPATH plasmid of Erwinia herbicola pv. gypsophilae determines host specificity.

The host range of the gall-forming bacterium Erwinia herbicola pv. gypsophilae (Ehg) is restricted to the gypsophila plant whereas E. herbicola pv. betae (Ehb) incites galls on beet as well as gypsophila. The pathogenicity of Ehg and Ehb was previously shown to be dependent on a plasmid (pPATH). Transposon mutagenesis was used to generate mutants on the cosmid pLA150 of the pPATH from Ehg824-1. A cluster of nonpathogenic mutations flanked by two IS1327 elements was identified on a 3.2-kb NdeI DNA fragment. All mutants were restored to pathogenicity by complementation in trans with the wild-type Ehg DNA. DNA sequence analysis of the 3.2-kb NdeI fragment revealed a single open reading frame (ORF) of 2 kb as well as a potential ribosome binding site and a putative hrp box upstream to the ORF. The ORF had no significant homology to known genes. Southern analysis also revealed the presence of DNA sequences that hybridized to the ORF in the beet pathovar Ehb4188. This gene was isolated and sequenced. Marker exchange mutants generated in the ORF of Ehb eliminated the pathogenicity of Ehb on gypsophila but fully retained its pathogenicity on beet. Since the putative gene appeared to encode a host-specific virulence factor for gypsophila it was designated as hsvG.

Amino Acid Sequence↗

Sequence variability, gene structure, and expression of full-length human endogenous retrovirus H.

Recently, we identified and classified 926 human endogenous retrovirus H (HERV-H)-like proviruses in the human genome. In this paper, we used the information to, in silico, reconstruct a putative ancestral HERV-H. A calculated consensus sequence was nearly open in all genes. A few manual adjustments resulted in a putative 9-kb HERV-H provirus with open reading frames (ORFs) in gag, pro, pol, and env. Long terminal repeats (LTRs) differed by 1.1%, indicating proximity to an integration event. The gag ORF was extended upstream of the normal myristylation start site. There was a long leader (including a "pre-gag" ORF) region positioned like the N terminus of murine leukemia virus (MLV) "glyco-Gag," potentially encoding a proline- and serine-rich domain remotely similar to MLV pp12. Another ORF, starting inside the 5' LTR, had no obvious similarity to known protein domains. Unlike other hitherto described gammaretroviruses, the reconstructed Gag had two zinc finger motifs. Alternative splicing of sequences related to the HERV-H consensus was confirmed using dbEST data. env transcripts were most prevalent in colon tumors, but also in normal testis. We found no evidence for full length env transcripts in the dbEST. HERV-H had a markedly skewed nucleotide composition, disfavoring guanine and favoring cytidine. We conclude that the HERV-H consensus shared a gene arrangement common to gammaretroviruses with gag separated by stop codon from pro-pol in the same reading frame, while env resides in another reading frame. There was also alternative splicing. HERV-H consensus yielded new insights in gammaretroviral evolution and will be useful as a model in studies on expression and function.

Amino Acid Sequence↗

Organizational characteristics and information content of an archaeal genome: 156 kb of sequence from Sulfolobus solfataricus P2.

We have initiated a project to sequence the 3 Mbp genome of the thermoacidophilic archaebacterium Sulfolobus solfataricus P2. Cosmids were selected from a provisional set of minimally overlapping clones, subcloned in pUC18, and sequenced using a hybrid (random plus directed) strategy to give two blocks of contiguous unique sequence, respectively, 100,389 and 56,105 bp. These two contigs contain a total of 163 open reading frames (ORFs) in 26-29 putative operons; 56 ORFs could be identified with reasonable certainty. Clusters of ORFs potentially encode proteins of glycogen biosynthesis, oxidative decarboxylation of pyruvate, ATP-dependent transport across membranes, isoprenoid biosynthesis, protein synthesis, and ribosomes. Putative promoters occur upstream of most ORFs. Thirty per cent of the predicted strong and medium-strength promoters can initiate transcription at the start codon or within 10 nucleotides upstream, indicating a process of initial mRNA-ribosome contact unlike that of most eubacterial genes. A novel termination motif is proposed to account for 15 additional terminations. The two contigs differ in densities of ORFs, insertion elements and repeated sequences; together they contain two copies of the previously reported insertion sequence ISC 1217, five additional IS elements representing four novel types, four classes of long non-IS repeated sequences, and numerous short, perfect repeats.

Chromosomes, Bacterial↗

Nucleotide sequence analysis of a cDNA clone encoding the 34K movement protein gene of odontoglossum ringspot virus, ORSV-Cy, the Korean isolate.

The partial nucleotide sequence of the 3'-terminal region of the Korean isolate of odontoglossum ringspot tobamovirus (ORSV-Cy) from cool-growing Cymbidium was determined. The sequence contained a full length open reading frame (ORF) coding for the viral cell-to-cell movement protein (MP). The ORF was located upstream of the coat protein gene and 105 nucleotides longer than that of tobacco mosaic virus (TMV). The ORF predicts a polypeptide chain of 303 amino acids with a molecular weight of 33573. The ORF contained a similar region of conserved sequence motif of tobamoviruses and putative assembly origin of the viral RNA was located at about 1,100 nucleotides away from the 3' end. The predicted amino acid sequence for the MP gene of ORSV-Cy is more closely related to pepper mild mottle virus (PMMV), TMV-vulgare and TMV-Rakkyo than to tobacco mild green mosaic virus (TMGMV), TMV-L, cowpea strain of TMV (SHMV), and cucumber green mottle mosaic virus (CGMMV).

Amino Acid Sequence↗

A new insertion variant, IS231I, isolated from a mosquito-specific strain of Bacillus thuringiensis.

A new insertion variant belonging to the family IS231, designated IS231I, was isolated from a mosquito larvicidal strain of the Bacillus thuringiensis serovar sotto (H4ab). IS231I was 1653 bp long and delimited by two 20 bp inverted repeats with one mismatch, flanked by two perfect 11 bp direct repeats. The element contained a single open reading frame (ORF) encoding 478 amino acids and five conserved domains: N1, N2, N3, C1, and C2. The 5' noncoding region upstream of the ORF, presumed to form a stable stem-and-loop structure, was highly conserved in IS231I. The secondary structure conformation had a deduced free energy (DeltaG=25 degrees C) of -17.2 kcal/mol. Comparison of the IS231I amino acid sequence with those of the 10 existing IS variants revealed that the new variant shares 89% identity with IS231A and IS231B, 65-66% with IS231M and IS231N, and 38% with IS231W.

Amino Acid Sequence↗

Chromosomal localization and genomic organization for the galactose/ N-acetylgalactosamine/N-acetylglucosamine 6-O-sulfotransferase gene family.

The galactose/N-acetylgalactosamine/N-acetylglucosamine 6-O-sulfotransferases (GSTs) are a family of Golgi-resident enzymes that transfer sulfate from 3'phosphoadenosine 5'phospho-sulfate to the 6-hydroxyl group of galactose, N-acetylgalactosamine, or N-acetylglucosamine in nascent glycoproteins. These sulfation modifications are functionally important in settings as diverse as cartilage structure and lymphocyte homing. To date six members of this gene family have been described in human and in mouse. We have determined the chromosomal localization of these genes as well as their genomic organization. While the broadly expressed enzymes implicated in proteoglycan biosynthesis are located on different chromosomes, the highly tissue specific enzymes GST-3 and 4 are encoded by genes located both in band q23.1--23.2 on chromosome 16. In the mouse, both genes reside in the syntenic region 8E1 on chromosome 8. This cross-species conserved clustering is suggestive of related functional roles for these genes. The human GST4 locus actually contains two highly similar open reading frames (ORF) that are 50 kb apart and encode two highly similar enzyme isoforms termed GST-4 alpha and GST-4 beta. All genes except GST0 (chondroitin 6-O-sulfotransferase) contain intron-less ORFs. With one exception these are fused directly to sequences encoding the 3' untranslated regions (UTR) of the respective mature mRNAs. The 5' UTRs of these mRNAs are usually encoded by a number of short exons 5' of the respective ORF. 5'UTRs of the same enzyme expressed in different cell types are sometimes derived from different exons located upstream of the ORF. The genomic organization of the GSTs resembles that of certain glycosyltransferase gene families.

Amino Acid Sequence↗

Conserved structure of IS200 elements in Salmonella.

Sequence analysis of three IS200 elements (two from Salmonella typhimurium, one from Salmonella abortusovis) reveals a highly conserved structure, with a length of 707-708 bp and absence of terminal repeats. IS200 contains an open-reading-frame (ORF) which potentially encodes a peptide of 151 amino acids, with a putative ribosome-binding-site properly placed upstream of the ORF. A potential RNA stem-loop structure that might occlude the ribosome-binding-site of the ORF is also found. Another conserved trait is a potential RNA hairpin which resembles a Rho-independent transcription terminator, located near one end of IS200. The junctions between IS200 and host DNA sequences are A+T-rich. Upon insertion, IS200 duplicates 1-2 bp of host DNA sequences. The observation that IS200 elements characterized as 'hops' are roughly identical to those residing in the Salmonella genome suggests that IS200 transposition is unlikely to generate inactive copies. If such is the case and many or all IS200 elements are active, the extremely low frequency of IS200 transposition may reflect the normal behavior of the element.

Amino Acid Sequence↗

A 55-kilodalton immunodominant antigen of Porphyromonas gingivalis W50 has arisen via horizontal gene transfer.

A 55-kDa outer membrane protein of Porphyromonas gingivalis W50 is a significant target of the serum immunoglobulin G antibody response of periodontal disease patients and hence may play an important role in host-bacterium interactions in periodontal disease. The gene encoding the 55-kDa antigen (ragB, for receptor antigen B) was isolated on a 9.5-kb partial Sau3AI fragment of P. gingivalis W50 chromosomal DNA in pUC18 by immunoscreening with a monoclonal antibody to this antigen. The 1.6-kb open reading frame (ORF) encoding RagB was located via subcloning and nested-deletion analysis. Sequence analysis demonstrated the presence of an upstream 3.1-kb ORF (ragA) which is cotranscribed with ragB. A number of genetic characteristics suggest that the ragAB locus was acquired by a horizontal gene transfer event. These include a significantly reduced G+C content relative to that of the P. gingivalis chromosome (42 versus 48%) and the presence of mobility elements flanking this locus in P. gingivalis W50. Furthermore, Southern blotting and PCR analyses showed a restricted distribution of this locus in laboratory and clinical isolates of this bacterium. The association of ragAB+ P. gingivalis with clinical status was examined by PCR analysis of subgingival samples. ragAB+ was not detected in P. gingivalis-positive shallow pockets from periodontal disease patients but was present in 36% of the P. gingivalis-positive samples from deep pockets. These data suggest that the ragAB locus was acquired by certain P. gingivalis strains via horizontal gene transfer and that the acquisition of this locus may facilitate the survival of these strains at sites of periodontal destruction.

Adult↗

The glnB region of the Escherichia coli chromosome.

We present sequences of the glnB gene of Escherichia coli and of two open reading frames (ORFs) located directly upstream of glnB and transcribed in the same direction. The major transcriptional start sites for glnB are located between ORF-2 and glnB, but some transcription of glnB is initiated at the promoter for ORF-1. The putative amino acid sequence of the ORF-2 product has high homology to that of response regulators which by phosphorylation acquire the ability to activate transcription of sigma 54-dependent promoters. The product of ORF-1 showed no similarity to other known proteins. The product of neither ORF-1 nor ORF-2 is necessary for the ability of PII, the product of glnB, to bring about the repression of glutamine synthetase in response to nitrogen excess. On the other hand, the product of hmpA, a gene located on the other side of glnB and transcribed in the opposite direction, appears to play an auxiliary role in this process.

Amino Acid Sequence↗

IS1549 from Mycobacterium smegmatis forms long direct repeats upon insertion.

A new insertion element, IS1549, was identified serendipitously from Mycobacterium smegmatis LR222 during experiments using a vector designed to detect the excision of IS6110 from between the promoter region and open reading frame (ORF) of an aminoglycoside phosphotransferase gene. Six of the kanamycin-resistant isolates had a previously unidentified insertion element upstream of the ORF of the aph gene. The 1,634-bp sequence contained a single ORF of 504 amino acids with 85% G+C content in the third codon position. The putative protein sequence showed a distant relationship to the transposase of IS231, which is a member of the IS4 family of insertion elements. IS1549 contains 11-bp terminal inverted repeats and is characterized by the formation of unusually long and variable-length (71- to 246-bp) direct repeats of the target DNA during transposition. Southern blot analysis revealed that five copies of IS1549 are present in LR222, but not all M. smegmatis strains carry this element. Only strains with a 65-kDa antigen gene with a PCR-restriction fragment length polymorphism type identical to that of M. smegmatis 607 contain IS1549. None of 13 other species of Mycobacterium tested by PCR with two sets of primers specific for IS1549 were positive for the expected amplified product.

Amino Acid Sequence↗

Novel genes affecting urease acivity in Actinobacillus pleuropneumoniae.

Characterization of a series of urease-negative transposon mutations of Actinobacillus pleuropneumoniae revealed that many of the mutants had insertions 2 to 4 kbp upstream of the urease gene cluster. A 5-kbp upstream region of DNA was sequenced and found to contain six open reading frames (ORFs) transcribed in the same orientation as the urease genes. As well, a partial ORF, apuR, 202 bp upstream of these six ORFs, is transcribed in the opposite orientation. The predicted product of this partial ORF shows homology with many members of the LysR family of transcriptional regulators. Five of the ORFs (cbiKLMQO) appear to form an operon encoding a putative nickel and cobalt periplasmic permease system. The cbiM and cbiQ genes encode proteins that have sequence similarity with known cobalt transport membrane proteins, and the cbiO gene encodes a cobalt transport ATP-binding protein homologue. The product of the cbiK gene is predicted to be the periplasmic-binding-protein component of the system, though it does not show any sequence similarity with CbiN, the cobalt-binding periplasmic protein. Escherichia coli clones containing this putative transport operon together with the urease genes of A. pleuropneumoniae were urease positive when grown in unsupplemented Luria-Bertani broth, whereas a clone containing only the minimal urease gene cluster required the addition of high concentrations of NiCl(2) for full urease activity. This result supports the hypothesis that nickel is a substrate for this permease system. The sixth ORF, utp, appears to encode an integral membrane protein which has significant sequence identity with mammalian urea transport proteins, though its function in A. pleuropneumoniae remains to be determined.

Actinobacillus pleuropneumoniae↗

Identification of a major, CsrRS-regulated secreted protein of Group A streptococcus.

CsrR/CsrS (CovR/CovS) is a two-component regulator of extracellular virulence factors in Group A streptococcus, but the full range of regulated exoproteins is unknown. Since CsrR represses expression of regulated factors, culture supernates of wild-type and CsrR(-)mutant strains were compared by two-dimensional gel electrophoresis (2DGE) to identify regulated exoproteins. Supernates of DeltacsrRS(-)mutant, but not wild-type, bacteria contained an abundant 23 kDa protein. The N-terminal sequence of this spot corresponded to a putative open reading frame (ORF) in the streptococcal genome. In a mobility shift assay, phosphorylated CsrR bound to a PCR amplicon that included sequences upstream of this ORF. By primer extension analysis, the ORF (designated mspA, for Mucoidy-associated Secreted Protein) was expressed in mid- and late-exponential phase in a DeltacsrRS(-)mutant. The presence of an in-frame deletion in mspA did not affect colony appearance, mucoidy or in vitro growth, and there was no difference between DeltamspA and wild-type strains in a mouse model of skin infection. MspA is co-regulated with other factors required for dermonecrosis (e.g. capsule, streptolysin S and purogenic exotoxin B); however, deletion of this gene does not affect expression of hyaluronic acid capsule or severity of skin infection in mice.

Animals↗

Molecular and immunological characterization of OprL, the 18 kDa outer-membrane peptidoglycan-associated lipoprotein (PAL) of Pseudomonas aeruginosa.

Immunological screening of a Pseudomonas aeruginosa cosmid library led to the identification of clones producing an 18 kDa outer-membrane protein. This protein reacted in Western blots with a polyclonal antiserum against outer-membrane proteins of P. aeruginosa and with a monoclonal antibody (MA1-6) specific for OprL, the peptidoglycan-associated outer-membrane lipoprotein (PAL). Sequencing of pOML7, a subclone expressing oprL, revealed an ORF of 504 bp encoding a polypeptide with a typical lipoprotein signal recognition sequence. Another ORF was found upstream of oprL, with homology to the TolB protein of Escherichia coli and Haemophilus influenzae. Downstream of oprL, a second ORF, of 321 bp, was found (orf2), encoding a protein with a signal peptide and with no homology with proteins of known biological function. After the stop codon of orf2, a rho-independent terminator sequence was detected which is part of the P. aeruginosa PAO1 insertion element IS222. OprL showed homologies with all known PALs from Gram-negative bacteria, especially in the C-terminal part. mAb MA1-6 reacted with P. aeruginosa cells in immunofluorescence, and with E. coli cells expressing oprL, which had an abnormal, elongated morphology, an indication that production of the protein perturbed the division process.

Amino Acid Sequence↗