Impact of smoking as a risk factor for developing rheumatoid arthritis: a meta-analysis of observational studies

OBJECTIVES

To assess whether smoking is a risk factor for developing rheumatoid arthritis (RA).

DESIGN

Meta-analysis.

METHOD

DATA SOURCES

were observational studies that examined the association between smoking history and the risk of developing RA identified through Medline and EMBASE (from 1966 to December 2006), relevant books and a reference search. Two authors independently extracted the following: authors' names, publication year, sample size, participant characteristics, odds ratios (OR) or relative risks, adjustment factors, study design and area where the study was conducted. Data syntheses were based upon random effects model. Summarised syntheses effects were expressed by OR.

RESULTS

Sixteen studies were selected from among 433 articles. For men, summary OR for ever, current and past smokers were 1.89 (95% CI 1.56 to 2.28), 1.87 (1.49 to 2.34) and 1.76 (1.33 to 2.31), respectively. For rheumatoid factor-positive (RF+) RA, summary OR for ever, current and past smokers were 3.02 (2.35 to 3.88), 3.91 (2.78 to 5.50) and 2.46 (1.74 to 3.47), respectively. Summary OR for 20 or more pack-years of smoking was 2.31 (1.55 to 3.41). For women, summary OR for ever, current and past smokers were 1.27 (1.12 to 1.44), 1.31 (1.12 to 1.54) and 1.22 (1.06 to 1.40), respectively. For RF+ RA, summary OR for ever, current and past smokers were 1.34 (0.99 to 1.80), 1.29 (0.94 to 1.77) and 1.21 (0.83 to 1.77). Summary OR for 20 or more pack-years of smoking was 1.75 (1.52 to 2.02).

CONCLUSION

Smoking is a risk factor for RA, especially RF+ RA men and heavy smokers.

Characterization of Fyn-mediated tyrosine phosphorylation sites on GluR epsilon 2 (NR2B) subunit of the N-methyl-D-aspartate receptor

The N-methyl-d-aspartate (NMDA) receptors play critical roles in synaptic plasticity, neuronal development, and excitotoxicity. Tyrosine phosphorylation of NMDA receptors by Src-family tyrosine kinases such as Fyn is implicated in synaptic plasticity. To precisely address the roles of NMDA receptor tyrosine phosphorylation, we identified Fyn-mediated phosphorylation sites on the GluR epsilon 2 (NR2B) subunit of NMDA receptors. Seven out of 25 tyrosine residues in the C-terminal cytoplasmic region of GluR epsilon 2 were phosphorylated by Fyn in vitro. Of these 7 residues, Tyr-1252, Tyr-1336, and Tyr-1472 in GluR epsilon 2 were phosphorylated in human embryonic kidney fibroblasts when co-expressed with active Fyn, and Tyr-1472 was the major phosphorylation site in this system. We then generated rabbit polyclonal antibodies specific to Tyr-1472-phosphorylated GluR epsilon 2 and showed that Tyr-1472 of GluR epsilon 2 was indeed phosphorylated in murine brain using the antibodies. Importantly, Tyr-1472 phosphorylation was greatly reduced in fyn mutant mice. Moreover, Tyr-1472 phosphorylation became evident when hippocampal long term potentiation started to be observed, and its magnitude became larger in murine brain. Finally, Tyr-1472 phosphorylation was significantly enhanced after induction of long term potentiation in the hippocampal CA1 region. These data suggest that Tyr-1472 phosphorylation of GluR epsilon 2 is important for synaptic plasticity.

Identification of the differential distribution patterns of mRNAs and consensus binding sequences for mouse DAF-16 homologues

daf-16 is a forkhead-type transcription factor, functioning downstream of insulin-like signals, and is known to be critical to the regulation of life span in Caenorhabditis elegans. Mammalian DAF-16 homologues include AFX, FKHR and FKHRL1, which contain a conserved forkhead domain and three putative phosphorylation sites for the Ser/Thr kinase Akt/protein kinase B (PKB), as well as for DAF-16. To assess the function of the homologues, we examined tissue distribution patterns of mRNAs for DAF-16 homologues in mice. In the embryos, expressions of AFX, FKHR and FKHRL1 mRNAs were complementary to each other and were highest in muscle, adipose tissue and embryonic liver. The characteristic expression pattern remained in the adult, except that signals of FKHRL1 became evident in more tissues, including the brain. In order to clarify whether each DAF-16 homologue had different target genes, we determined the consensus sequences for the binding of DAF-16 and the mouse homologues. The binding sequences for all four proteins shared a core sequence, TTGTTTAC, daf-16 family protein-binding element (DBE) binding protein. However, electrophoretic mobility shift assay showed that the binding affinity of DAF-16 homologues to the core sequence was stronger than that to the insulin-responsive element in the insulin-like growth factor binding protein-1 promoter region, which has been identified as a binding sequence for them. We identified one copy of the DBE upstream of the first exon of sod-3 by searching the genomic database of C. elegans. Taken together, DAF-16 homologues can fundamentally regulate the common target genes in insulin-responsive tissues and the specificity to target genes of each protein is partially determined by the differences in their expression patterns.

Humoral immune response to hypervariable region 1 of the putative envelope glycoprotein (gp70) of hepatitis C virus

We recently found that alterations of amino acids in hypervariable region 1 (HVR1) of the putative envelope glycoprotein (gp70) of hepatitis C virus (HCV) occurred sequentially in the chronic phase of hepatitis at intervals of several months. This finding suggests that mutations in HVR1 are involved in the mechanism of persistent chronic HCV infection involving escape from the immunosurveillance system. To explore this possibility, we examined the humoral immune response to HVR1 with our assay system, in which immunoprecipitation was carried out with sera from patients by using an HVR1 (27-amino-acid) dihydrofolate reductase fusion protein synthesized by in vitro transcription and translation. Results showed that HVR1 contains a sequence-specific immunological epitope that induces the production of antibodies restricted to the specific viral isolate. Furthermore, analysis of the kinetics of the appearance of antibodies in two patients with chronic hepatitis, with whom successive alterations of amino acids of HVR1 have been observed, showed that the titers of anti-HVR1 antibodies usually reached maximal levels several months after the isolation of HCV having the specific sequence of HVR1. This observation suggests that anti-HVR1 antibodies are involved in the genetic drift of HVR1 (minor antigenic variation) by immunoselection. However, the coexistence of HVR1 as an antigen and its specific antibody was sometimes observed. The possibility that HVR1 acts as a neutralizing epitope is discussed.

Hydrogen peroxide secreted by tumor-derived macrophages down-modulates signal-transducing zeta molecules and inhibits tumor-specific T cell-and natural killer cell-mediated cytotoxicity

Although alterations in CD3-associated signal-transducing molecules in tumor-infiltrating T cells of patients with advanced cancer have been previously described, the mechanism behind these changes is not known. We demonstrate that macrophages isolated from metastatic lymph nodes of patients with malignant melanoma down-regulate levels of CD3 zeta in autologous peripheral blood T cells. Lipopolysaccharide (LPS)- or phorbol 12-myristate 13-acetate (PMA)-stimulated monocytes derived from peripheral blood of healthy donors also induced decreased expression of CD3 and CD16-associated zeta chains similar to that observed in T cells and natural killer (NK) cells of patients with advanced cancer. Co-culture with activated monocytes impaired Ca2+ mobilization in peripheral blood derived-T cells when stimulated with monoclonal antibodies to CD3 and also strongly inhibited melanoma-specific cytotoxic T lymphocyte (CTL) activity and NK activity. The presence of catalase, a scavenger of H2O2, during co-culture almost totally abrogated the inhibitory effect of activated monocytes on melanoma-specific CTL lines and on NK cells. Pre-treatment of CTL or NK cells with nontoxic concentrations (1 x 10(-5) M) of H2O2 also severely reduced their cytotoxic activity which could be prevented by catalase. The decrease in CD3 zeta and in CD16 zeta expression, induced by macrophages isolated from metastatic lymph nodes or by LPS-stimulated monocytes, was also prevented by catalase when maintained throughout the co-culture period. The possibility that monocyte/macrophage-derived reactive oxygen metabolites contribute directly to alterations in signal transducing molecules of T cells and NK cells and to the mechanism of immunosuppression in individuals with cancer should be considered.

B cell subpopulations separated by CD27 and crucial collaboration of CD27+ B cells and helper T cells in immunoglobulin production

B cell immunoglobulin production is regulated by helper T cells through direct interaction and secreted cytokines. In the present study, we functionally analyzed CD27 in cord and peripheral blood B cells. Adult peripheral blood B cells were separated into CD27+ and CD27- cells, which differed in their morphology. Cord blood B cells did not express CD27, and CD27 expression on peripheral blood B cells increased with age. Only CD27+ B cells had the ability to produce immunoglobulin, which was increased by contact with a tumor necrosis factor-related transmembrane ligand, CD70. Adult peripheral blood CD27+ B cells can be further subdivided into two discrete subtypes: IgD- CD27+ and IgD+ CD27+ B cells. IgD- CD27+ B cells produce IgG, IgM and IgA, whereas IgD+ CD27+ B cells predominantly produce IgM. The addition of activated CD4+ CD45RO T cells expressing CD70 caused down-regulation of CD27 expression on activated B cells, and this down-modulation was completely blocked by anti-CD70 monoclonal antibody, indicating direct T-B cell contact via CD27/CD70. The triggering via CD27 and CD40 additively increased the immunoglobulin production under Staphylococcus aureus Cowan strain plus interleukin-2 stimulation. Taken together, our findings demonstrate that peripheral blood B cells are separated into subpopulations by CD27 and IgD expression and that CD27+ B cells produce large amounts of immunoglobulin by interaction with the CD70 molecule.

A urease-negative mutant of Helicobacter pylori constructed by allelic exchange mutagenesis lacks the ability to colonize the nude mouse stomach

The urease of Helicobacter pylori has been proposed to be one of its pathogenic factors. A kanamycin resistance determinant was inserted in a cloned urease gene, and transformation-mediated allelic exchange mutagenesis was carried out to introduce the disrupted gene into the corresponding wild-type chromosomal region of a clinical isolate of H. pylori, CPY3401. The resulting mutant, HPT73, had the null activity of urease. Nude mouse stomachs were challenged with these two isogenic strains to examine the role of urease in pathogenesis. Gastritis was found in the CPY3401-challenged stomachs, from which bacteria indistinguishable from CPY3401 were recovered. There was no gastritis in the HPT73-challenged stomachs, and we could not recover H. pylori from them. These results indicated that H. pylori urease is essential for colonizing the nude mouse stomach.

Differences in genotypes of Helicobacter pylori from different human populations

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.

Extracellular accumulation of glutamate in the hippocampus induced by ischemia is not calcium dependent--in vitro and in vivo evidence

Calcium dependency of ischemia-induced increase in extracellular glutamate in the hippocampus was studied in vitro and in vivo. Perfusion of a low pO2 medium without glucose (in vitro ischemia) induced an increase in extracellular glutamate in rat hippocampal slices. This increase did not depend on Ca2+, which is in contrast with the observation that about 40% of membrane depolarization (50 mM KCl)-evoked release was Ca2+-dependent. In vivo cerebral ischemia of 5 min duration in gerbils also caused Ca2+-independent increase in extracellular glutamate in the hippocampus. The data suggest that the increase in extracellular glutamate induced by ischemia is not due to the enhanced release of neurotransmitter glutamate.

Relaxation of contracted rabbit tracheal and human bronchial smooth muscle by Y-27632 through inhibition of Ca2+ sensitization

The mechanism of Ca2+ sensitization of contraction has not been elucidated in airway smooth muscle (SM). To determine the role of a small G protein, rhoA p21, and its target protein, rho-associated coiled coil-forming protein kinase (ROCK), in receptor-coupled Ca2+ sensitization of airway SM, we studied the effect of (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexane carboxamide dihydrochloride, monohydrate (Y-27632), a ROCK inhibitor, on isometric contractions in rabbit tracheal and human bronchial SM. Y-27632 completely reversed 1 microM carbachol (CCh)-induced contraction of intact trachea with a concentration producing half-maximum inhibition of effect (IC50) of 1.29 +/- 0.2 microM (n = 5). Although 4beta-phorbol 12,13-dibutyrate (1 microM)-induced Ca2+ sensitization was relatively resistant to Y-27632 in alpha-toxin-permeabilized trachea, CCh (100 microM) plus guanosine triphosphate (GTP) (3 microM)- and guanosine 5'-O-(3'-thiotriphosphate) (10 microM)-induced contractions were relaxed completely by Y-27632 with IC50 of 1.44 +/- 0.3 (n = 6) and 1.15 +/- 0.3 microM (n = 6). Endothelin-1 (1 microM) plus GTP (3 microM)- developed force was also reversed by Y-27632 with IC50 of 4. 10 +/- 1.1 microM (n = 6) in the alpha-toxin-permeabilized bronchus. Both the rabbit and human SM expressed rhoA p21, ROCK I, and its isoform ROCK II. Collectively, rho/ROCK-mediated Ca2+ sensitization plays a central role in the sustained phase of airway SM contraction, and selective inhibition of this pathway may become a new strategy to resolve airflow limitation in asthma.

Marked sequence diversity in the putative envelope proteins of hepatitis C viruses

The nucleotide sequences of cDNAs (414 base pairs) encoding parts of putative envelope proteins (gp35 and gp70) of 40 isolates of hepatitis C virus (HCV-J) derived from 30 independent plasma or liver specimens from Japanese patients (13 with chronic hepatitis, 14 with hepatocellular carcinoma and 3 hemophiliacs who had received imported clotting factors), were analyzed using the polymerase chain reaction. Approximately 29-38% of the nucleotide sequences of the HCV-J isolates examined differed from those of isolates from the United States (HCV-US). Furthermore, 12-24% and 8-17% sequence diversities were found within the isolates of HCV-J and HCV-US, respectively. The diversities of the amino acid sequences were the same or greater than those of the nucleotide sequences. We confirmed that two hypervariable regions (HVR1 and HVR2) were present in this amplified region, as described in our previous report (Hijikata et al., 1991a) and we found that the HVR1 regions of HCV-J and HCV-US were 27 and 21 amino acids in length, respectively, and began from the N-terminal amino acid of gp70. HVR2 was found in HCV-J, but not in HCV-US isolates, in which the corresponding region of the genome was conserved. During the analysis, plural HCV genomes were found in 6 of 30 specimens. These plural HCV genomes in a single specimen were concluded to be derived from the same HCV ancestor, because of their relative low sequence diversities (about 10% in their nucleotide sequences).(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic drift in hypervariable region 1 of the viral genome in persistent hepatitis C virus infection

The hypervariable region 1 (HVR1) of the putative second envelope glycoprotein (gp70) of hepatitis C virus (HCV) contains a sequence-specific immunological B-cell epitope that induces the production of antibodies restricted to the specific viral isolate, and anti-HVR1 antibodies are involved in the genetic drift of HVR1 driven by immunoselection (N. Kato, H. Sekiya, Y. Ootsuyama, T. Nakazawa, M. Hijikata, S. Ohkoshi, and K. Shimotohno, J. Virol. 67:3923-3930, 1993). We further investigated the sequence variability of the HCV genomic region that entirely encodes the envelope proteins (gp35 and gp70); these sequences were derived from virus isolated during the acute and chronic phases of hepatitis in one patient, and we found that HVR1 was a major site for genetic mutations in HCV after the onset of hepatitis. We carried out epitope-mapping experiments using the HVR1 sequence derived from the acute phase of hepatitis and identified two overlapping epitopes which are each composed of 11 amino acids (positions 394 to 404 and 397 to 407). The presence of two epitopes within HVR1 suggested that epitope shift happened during the course of hepatitis. Four of six amino acid substitutions detected in HVR1 were located within the two epitopes. We further examined the reactivities of anti-HVR1 antibodies to the substituted amino acid sequences within the two epitopes. HVR1 variants in both epitopes within the HVR1 escaped from anti-HVR1 antibodies that were preexisting in the patient's serum.

Identification of the urease operon in Helicobacter pylori and its control by mRNA decay in response to pH

We investigated the transcription of the urease gene cluster ureABIEFGH in Helicobacter pylori to determine the regulation of gene expression of the highly produced enzyme urease. Northern blot hybridization analysis demonstrated that cells of the wild-type strain grown in an ordinary broth had transcripts of ureAB, ureABI, ureI, ureIE' and ure'FGH, but cells of a ureI-disrupted mutant had only the ureAB transcript. When the wild-type cells were exposed to pH 8 for 30 min, very little mRNA was detected. However, when exposed to pH 6, a large amount of the ureIE" transcript, which was longer than the ureIE' transcript, together with the additional transcripts ureABIEFGH and ure'EFGH were detected. Rifampicin addition experiments demonstrated that urease mRNAs, and the ureIE' transcripts in particular, are more stable at pH 5.5 than at pH 7. In accord with these results, urease activity in the crude cell extract of the pH 5.5 culture was twice as much as that of the pH 7 culture, although the amounts of UreA and UreB detected by immunoblot analysis were similar. The transcription start point of ureI was identified by primer extension using a ureA promoter-deleted mutant, and a consensus sequence of RpoD-RNA polymerase was found in the ureI promoter. The 3' end of the ureIE" mRNA, determined using S1 nuclease mapping, revealed that the transcript is able to cover the majority of the ureE open reading frame (ORF) that might be sufficient for UreE activity. Based on the above results, we conclude that the urease gene cluster of H. pylori consists of two operons, ureAB and ureIEFGH, and that primary transcripts of the latter as well as the read-through transcript, ureABIEFGH, are cleaved to produce several species of mRNA. It has been suggested that the ureIEFGH operon is regulated post-transcriptionally by mRNA decay in response to environmental pH. We are tempted to speculate that the ureE" transcript present in acidic pH may contribute to produce an active product that can proceed the nickel incorporation to the active centre, the final step of urease biosynthesis.

Comparison of whole genome sequences of Chlamydia pneumoniae J138 from Japan and CWL029 from USA

Chlamydia pneumoniae is a widespread pathogen of humans causing pneumonia and bronchitis. There are many reports of an association between C.PNEUMONIAE: infection and atherosclerosis. We determined the whole genome sequence of C.PNEUMONIAE: strain J138 isolated in Japan in 1994 and compared it with the sequence of strain CWL029 isolated in the USA before 1987. The J138 circular chromosome consists of 1 226 565 nt (40.7% G+C) with 1072 likely protein-coding genes that is 3665 nt shorter than the CWL029 genome. Plasmids, phage- or transposon-like sequences were not identified. The overall genomic organization, gene order and predicted proteomes of the two strains are very similar, suggesting a high level of structural and functional conservation between the two unrelated isolates. The most conspicuous differences in the J138 genome relative to the CWL029 genome are the absence of five DNA segments, ranging in size from 89 to 1649 nt, and the presence of three DNA segments, ranging from 27 to 84 nt. The complex organization of these 'different zones' may be attributable to a unique system of recombination.

Molecular cloning of hepatitis C virus genome from a single Japanese carrier: sequence variation within the same individual and among infected individuals

A hepatitis C virus (HCV) genome was isolated and sequenced from a single Japanese patient with chronic non-A, non-B hepatitis. The genome (HCV-JT), which was constructed with 23 cDNA clones, consisted of 9436 nucleotides with a long open reading frame which could encode a sequence of 3010 amino acid residues. To study the sequence variation of the HCV genome in an individual, we analyzed another sequence of the HCV genome (HCV-JT') constructed with different cDNA clones derived from the same patient. The nucleotide variation between HCV-JT and -JT' was less than 1%, and was distributed throughout the genome except in the 5' non-coding region, where no variation was observed. The diversity was higher (1.6%) in the putative envelope protein region than in other regions. The nucleotide and deduced amino acid sequences of HCV-JT showed homologies of about 91 and 95%, respectively, with those of other Japanese HCV isolates. The nucleotide diversity was high in the gp 70 region (corresponding to the NS 1 region of flaviviruses) and low in the 5' non-coding and p22 (putative core protein) regions. A similar pattern of distribution of nucleotide changes was observed on comparison of HCV-JT with an American isolate HCV-US, where the homologies in nucleotide and amino acid sequences were about 79 and 85%, respectively. Base transversions contributed about 50% of the total base exchanges between the Japanese and American HCV sequences, but only 20% or less of those among Japanese HCV or among American HCV sequences. Thus, the Japanese and American HCVs are genetically distinguishable, supporting our earlier prediction that these two HCVs could be classified as different subtypes.

Conversion from farnesyl diphosphate synthase to geranylgeranyl diphosphate synthase by random chemical mutagenesis

Prenyltransferases catalyze the consecutive condensation of isopentenyl diphosphate (IPP) with allylic diphosphates to produce prenyl diphosphates whose chain lengths are absolutely determined by each enzyme. In order to investigate the mechanisms of the consecutive reaction and of the determination of ultimate chain length, a random mutational approach was planned. The farnesyl diphosphate (FPP) synthase gene of Bacillus stearothermophilus was subjected to random mutagenesis by NaNO2 treatment to construct libraries of mutated FPP synthase genes on a high-copy plasmid. From the libraries, the mutants that showed the activity of geranylgeranyl diphosphate (GGPP) synthase were selected by the red-white screening method (Ohnuma, S.-i., Suzuki, M., and Nishino, T. (1994) J. Biol. Chem. 268, 14792-14797), which utilized carotenoid synthetic genes, phytoene synthase, and phytoene desaturase, to visualize the formation of GGPP in vivo. Eleven red positive clones were identified from about 24,300 mutants, and four (mutant 1, 2, 3, and 4) of them were analyzed for the enzyme activities. Results of in vitro assays demonstrated that all these mutants produced (all-E)-GGPP although the amounts were different. Each mutant was found to contain a few amino acid substitutions: mutant 1, Y81H and L275S; mutant 2, L34V and R59Q; mutant 3, V157A and H182Y; mutant 4, Y81H, P239R, and A265T. Site-directed mutagenesis showed that Y81H, L34V, or V157A was essential for the expression of the activity of GGPP synthase. Especially, the replacement of tyrosine 81 by histidine is the most effective because the production ratios of GGPP to FPP in mutant 1 and 4 are the largest. Based on prediction of the secondary structure, it is revealed that the tyrosine 81 situates on a point 11 approximately 12 A apart from the first DDXXD motif, whose distance is similar to the length of hydrocarbon moiety of FPP. These data might suggest that the aromatic ring of tyrosine 81 blocks the chain elongation longer than FPP. Comparisons of kinetic parameters of the mutated and wild type enzymes revealed several phenomena that may relate with the change of the ultimate chain length. They are a decrease of the total reaction rate, increase of Kmfor dimethylallyl diphosphate, decrease of Vmax for dimethylallyl diphosphate, and allylic substrate dependence of Km for IPP.

Transgenic mice overexpressing type 2 nitric-oxide synthase in pancreatic beta cells develop insulin-dependent diabetes without insulitis

We generated transgenic mice carrying the mouse type 2 nitric-oxide synthase (NOS2) cDNA under the control of the insulin promoter. Western and immunohistochemical analyses revealed that NOS2 was expressed abundantly in transgenic islets but not in control islets. When islets were isolated and cultured, high levels of nitrite were released from the transgenic islets. In transgenic mice, the beta cell mass was markedly reduced without the infiltration of macrophages or lymphocytes, and extensive DNA strand breaks were detected in the islets by in situ nick translation. All the transgenic mice developed hypoinsulinemic diabetes by 4 weeks of age, and treatment with an inhibitor of NOS2, aminoguanidine (200 mg/kg body weight every 12 h), prevented or delayed the development of diabetes. The present study shows that the production of nitric oxide by beta cell NOS2 plays an essential role in the beta cell degeneration.

Nucleotide sequence of the structural gene for colicin E1 and predicted structure of the protein

We have determined the nucleotide sequence of the structural gene for colicin E1, which consists of 1,566 base pairs. The amino acid sequence (522 residues) of the protein was derived from the DNA sequence, and the molecular weight was calculated to be 57,279. From the analysis of the predicted secondary structure, there appear to be three consecutive long alpha-helices in the NH2-terminal half of the polypeptide, spanning 40, 100, and 35 amino acid residues. In addition, there is a polypeptide region near the COOH terminus that shows homology to the NH2-terminal signal portions of outer membrane lipoprotein in Escherichia coli and beta-lactamase in Bacillus licheniformis. Most of the homologous amino acids are located in the region where either alpha-helix or beta-sheet would be expected to occur, as determined from the amino acid sequence. These characteristics of the predicted protein structure might correspond to properties of colicin E1 as an ionophore in its antimicrobial action and also as an exported protein during its induced synthesis.

Molecular cloning of regulatory gene xylR and operator-promoter regions of the xylABC and xylDEGF operons of the TOL plasmid

The regulatory gene xylR of the TOL plasmid, which functions positively on both xylABC and xylDEGF operons in the presence of m-xylene or m-methylbenzyl alcohol, was cloned onto an Escherichia coli vector, pACYC177. A fused operon consisting of the operator-promoter region of the xylABC operon and the xylE gene was cloned onto pBR322. The xylE product, catechol 2,3-dioxygenase, was induced by m-xylene or m-methylbenzyl alcohol in the cells containing the fused operon when a 2.8-kilobase segment of the TOL plasmid was provided in trans. Therefore, the segment appeared to contain the regulatory gene xylR. The xylR gene was mapped very close to the other regulatory gene, xylS, determined previously. The xylR gene was not effective on activation of the xylDEGF operon unless an additional region containing xylS was provided together with the inducer. These results indicate that both xylR and xylS are essential to the m-methylbenzyl alcohol-dependent induction of the xylDEGF operon. The map positions of xylR and xylS were precisely determined by subcloning or insertion inactivation. In addition, the operator-promoter regions of the xylABC and xylDEGF operons were mapped to the 0.6- and 0.4-kilobase regions of the TOL plasmid, respectively.

Characterization of hypervariable regions in the putative envelope protein of hepatitis C virus

We previously identified two hypervariable regions [HVR1 (27 amino acids) and HVR2 (7 amino acids)] in the putative envelope glycoprotein (gp70) by comparison of the amino acid sequences of many isolates of the HCV-II genotype. To understand the functional features of these HVRs, using the polymerase chain reaction we analyzed the rate of actual sequence variability in the region including HVR1 and HVR2 of HCV isolated successively at intervals of several months from two patients with chronic C-type hepatitis. In both patients, the amino acid sequence of HVR1, but not HVR2, was found to change dramatically during the observation period (about one amino acid per month). However, no alteration of the amino acid sequence of HVR1 of HCV was observed in a patient in the acute phase of chronic hepatitis. Restriction digestion analysis of sequence diversity showed that a HCV genome with a newly introduced mutation in HVR1 often became the predominant population at the next time of examination. Alterations of amino acids in HVR1 occurred sequentially in the two patients in the chronic phase. These findings suggest that mutations in HVR1 are involved in the mechanism of persistent chronic HCV infection.

Benzoate metabolism in Pseudomonas putida(arvilla) mt-2: demonstration of two benzoate pathways

Benzoate-grown cells of Pseudomonas putida(arvilla) mt-2 contain both metapyrocatechase and pyrocatechase activities, although the former activity is much higher than that of the latter. A spontaneous mutant deficient in metapyrocatechase and 2-hydroxymuconic semialdehyde hydrolyase, the first two enzymes in the meta-cleavage pathway of the ring of catechol, has been isolated from this strain. This mutant grows well on a minimal medium containing benzoate as a sole carbon source and has the high activity of pyrocatechase. These findings indicate that the strain mt-2 possesses the genetic capacity for enzymes of both the meta- and ortho-cleavage pathways of benzoate degradation, but its phenotypic expression is the meta pathway.

Molecular cloning of gene xylS of the TOL plasmid: evidence for positive regulation of the xylDEGF operon by xylS

The xylDEGF operon and the regulatory gene xylS of the TOL plasmid found in Pseudomonas putida mt-2 were cloned onto Escherichia coli vector plasmids. A 9.5-kilobase fragment, derived from the TOL segment of pTN2 deoxyribonucleic acid, carried the xyl genes D, E, G, and F, which encode toluate oxygenase, catechol 2,3-oxygenase, 2-hydroxymuconic semialdehyde dehydrogenase, and 2-hydroxymuconic semialdehyde hydrolase, respectively. The enzymes were noninducible unless a 3-kilobase PstI fragment, derived also from the TOL segment, was provided in either cis or trans. The PstI fragment appeared to contain the regulatory gene xylS, which produced a positive regulator. The regulator was activated by m-toluate or benzoate, but not by m-xylene or m-methylbenzyl alcohol. the map positions of xylG and xylF were also determined.