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New killing system controlled by two genes located immediately upstream of the mukB gene in Escherichia coli.

The nucleotide sequence was determined of the region upstream of the mukB gene of Escherichia coli. Two new genes were found, designated kicA and kicB (killing of cell); the gene order is kicB-kicA-mukB. Promoter activities were detected in the regions immediately upstream of kicB and kicA, but not in front of mukB. Gene disruption experiments revealed that the kicA disruptant was nonviable, but the kicB-disrupted mutant and the mutant lacking both the kicB and kicA genes were able to grow. When kicA disruptant cells bearing a temperature-sensitive replication plasmid carrying the kicA+ gene were grown at 30 degrees C and then transferred to 42 degrees C, the mutant cells gradually lost colony-forming ability, even in the presence of a mukB+ plasmid. Rates of protein synthesis, but not of RNA or DNA synthesis, fell dramatically during incubation at 42 degrees C. These results suggested that the kicB gene encodes a killing factor and the kicA gene codes for a protein that suppresses the killing function of the kicB gene product. It was also demonstrated that KicA and KicB can function as a post-segregational killing system, when the genes are transferred from the E. coli chromosome onto a plasmid.

Amino Acid Sequence↗

A Sordaria macrospora mutant lacking the leu1 gene shows a developmental arrest during fruiting body formation.

Developmental mutants with defects in fruiting body formation are excellent resources for the identification of genetic components that control cellular differentiation processes in filamentous fungi. The mutant pro4 of the ascomycete Sordaria macrospora is characterized by a developmental arrest during the sexual life cycle. This mutant generates only pre-fruiting bodies (protoperithecia), and is unable to form ascospores. Besides being sterile, pro4 is auxotrophic for leucine. Ascospore analysis revealed that the two phenotypes are genetically linked. After isolation of the wild-type leu1 gene from S. macrospora, complementation experiments demonstrated that the gene was able to restore both prototrophy and fertility in pro4. To investigate the control of leu1 expression, other genes involved in leucine biosynthesis specifically and in the general control of amino acid biosynthesis ("cross-pathway control") have been analysed using Northern hybridization and quantitative RT-PCR. These analyses demonstrated that genes of leucine biosynthesis are transcribed at higher levels under conditions of amino acid starvation. In addition, the expression data for the cpc1 and cpc2 genes indicate that cross-pathway control is superimposed on leucine-specific regulation of fruiting body development in the leu1 mutant. This was further substantiated by growth experiments in which the wild-type strain was found to show a sterile phenotype when grown on a medium containing the amino acid analogue 5-methyl-tryptophan. Taken together, these data show that pro4 represents a novel mutant type in S. macrospora, in which amino acid starvation acts as a signal that interrupts the development of the fruiting body.

3-Isopropylmalate Dehydrogenase↗

Cloning, expression and sequence analysis of an endolysin-encoding gene of Lactobacillus bulgaricus bacteriophage mv1.

The lysA gene specifying an endolysin of Lactobacillus delbrueckii subsp. bulgaricus bacteriophage mv1, was cloned and expressed in Escherichia coli. The 4.05-kb restriction fragment containing this gene was analysed by restriction and deletion mapping, and by subcloning. The nucleotide sequence of a 1150-bp fragment coding for an active lysin was determined. The lysA gene consists of 585 bp and codes for a protein of a deduced Mr of 21,120, which agrees with the size based on in vivo transcription/translation studies. The deduced amino acid sequence of the mv1 lysin (LysA) was compared to that of other known lytic enzymes. Significant homology was observed with the N-terminal portion of the muramidase of the fungus Chalaropsis and that of the muramidase of the Streptococcus pneumoniae phage Cp-1, suggesting that LysA might be a muramidase. In E. coli, the cloned lysA gene was able to complement the muramidase-defective bacteriophage lambda Ram5, proving that the products of these two genes are interchangeable. The lysA gene is preceded by an open reading frame with unknown function and no characteristic prokaryotic promoter sequences could be detected upstream from lysA, suggesting that this gene is part of an operon.

Amino Acid Sequence↗

Multiple human papillomavirus genes affect the adeno-associated virus life cycle.

The risk of cervical cancer, one of the most prevalent cancers in the world, is determined by two viruses. Human papillomavirus (HPV) is the main risk factor for developing cervical cancer. However, although little known, it is well substantiated that the human Parvovirus adeno-associated virus type 2 (AAV), and its encoded Rep78 protein, interacts with HPV and lowers the risk of cervical cancer. HPV also contributes to AAV inhibition by serving as a helper virus for AAV and stimulating higher AAV replication levels. Here we surveyed four HPV-16 early genes, E1, E2, E6 and E7, for their ability to increase/decrease the basal level of AAV replication in stratifying squamous epithelium (the epithelial raft culture system). It was found that the HPV-16 E1, E2 and E6 genes were able to help/enhance AAV-2 replication in epithelial raft cultures. Under these conditions, with all the HPV genes being expressed from the AAV p5 promoter, E1 appeared to have the strongest enhancing effect on AAV DNA replication (Southern blot), RNA expression (RT-PCR), protein expression (Western blot) and AAV virion production (2 plate-Southern blot). Further study of E1 mutants showed that the carboxy-half of E1, the putative helicase/ATPase domain, was the main contributor of helper activity. These data are important for understanding the HPV-AAV interaction and its effect on modifying cervical cancer risk. These data also suggest the possibility that the identified HPV helper genes may be useful in the generation of recombinant (r)AAV virions for gene therapy, as rAAV is increasing in popularity for such purposes.

Capsid Proteins↗

The human formin-binding protein 17 (FBP17) interacts with sorting nexin, SNX2, and is an MLL-fusion partner in acute myelogeneous leukemia.

We have cloned a fusion partner of the MLL gene at 11q23 and identified it as the gene encoding the human formin-binding protein 17, FBP17. It maps to chromosome 9q34 centromeric to ABL. The gene fusion results from a complex chromosome rearrangement that was resolved by fluorescence in situ hybridization with various probes on chromosomes 9 and 11 as an ins(11;9)(q23;q34)inv(11)(q13q23). The rearrangement resulted in a 5'-MLL/FBP17-3' fusion mRNA. We retrovirally transduced murine-myeloid progenitor cells with MLL/FBP17 to test its transforming ability. In contrast to MLL/ENL, MLL/ELL and other MLL-fusion genes, MLL/FBP17 did not give a positive readout in a serial replating assay. Therefore, we assume that additional cooperating genetic abnormalities might be needed to establish a full malignant phenotype. FBP17 consists of a C-terminal Src homology 3 domain and an N-terminal region that is homologous to the cell division cycle protein, cdc15, a regulator of the actin cytoskeleton in Schizosaccharomyces pombe. Both domains are separated by a consensus Rho-binding motif that has been identified in different Rho-interaction partners such as Rhotekin and Rhophilin. We evaluated whether FBP17 and members of the Rho family interact in vivo with a yeast two-hybrid assay. None of the various Rho proteins tested, however, interacted with FBP17. We screened a human kidney library and identified a sorting nexin, SNX2, as a protein interaction partner of FBP17. These data provide a link between the epidermal growth factor receptor pathway and an MLL fusion protein.

Artificial Gene Fusion↗

Selection for conditional gametogenesis in Chlamydomonas reinhardi.

A new technique is described for selection of temperature-sensitive mutants affecting gametogenesis in Chlamydomonas reinhardi. The first mutant found by this technique is characterized. Cells exhibiting the gam-1 phenotype are capable of sexual agglutination, but cannot form zygotes at the restrictive temperature. The mutation, however, has been expressed only in gametes of mating type (-). Cells of mating type (+) which carry this gene are able to engage in normal zygote formation. Temperature shift experiments and antibiotic studies have indicated that this gene is expressed within 6 hr after the onset of gametogenesis in liquid culture, and its product has a lifetime of about 4 hr at 35 degrees.

Chlamydomonas↗

Characterization of mercury resistance mechanisms in marine sediment microbial communities.

While estuarine sediments are often severely polluted with mercury, few studies have focused on the mechanisms of adaptation to mercury contamination in marine sediment microbial communities. In this study, we report a high frequency of Gram-negative bacterial isolates that are resistant to the heavy metal mercury obtained from the aerobic culturable marine microbial community. We detected a low frequency of genes homologous to mer(Tn21) in isolates from three out of four different estuarine environments. Other mercury resistant culturable bacterial isolates lacking homology to the known mer genes were able to reduce Hg(II) to its volatile Hg(0) form, indicating the presence of divergent mer genes. In addition, a number of mercury resistant isolates, obtained from three of the four marine sites investigated, exhibited decreased resistance to mercury in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone. Representative mercury resistant bacterial isolates were identified by phylogenetic analysis as belonging to the alpha and gamma subclasses of the class Proteobacteria.

Journal Article↗

Characterization of a WaaF (RfaF) homolog expressed by Haemophilus ducreyi.

Haemophilus ducreyi lipooligosaccharide (LOS) is capable of inducing an inflammatory response in skin (A. A. Campagnari, L. M. Wild, G. Griffiths, R. J. Karalus, M. A. Wirth, and S. M. Spinola, Infect. Immun. 59:2601-2608, 1991) and likely contributes to the virulence of this sexually transmitted pathogen (B. A. Bauer, M. K. Stevens, and E. J. Hansen, Infect. Immun. 68:4290-4298, 1998). An open reading frame in H. ducreyi 35000 was found to encode a predicted protein that was 59% identical to the protein product of the rfaF (waaF) gene of Salmonella typhimurium. The H. ducreyi waaF gene was able to complement an S. typhimurium rfaF (waaF) mutant, a result which confirmed the identity of this gene. In contrast to the rfaF (waaF) gene of enteric bacteria, the H. ducreyi waaF gene was not located adjacent to other genes involved in lipopolysaccharide expression. Inactivation of the H. ducreyi waaF gene by insertion mutagenesis resulted in expression of a LOS that migrated much faster than wild-type LOS in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The LOS of this mutant also did not bind a monoclonal antibody directed against a cell surface-exposed epitope of wild-type H. ducreyi LOS. Testing of the wild-type H. ducreyi strain and its isogenic waaF mutant in the temperature-dependent rabbit model for dermal lesion production by H. ducreyi revealed that this waaF mutant was less virulent than the wild-type parent strain. Complementation of the H. ducreyi waaF mutant with the wild-type H. ducreyi waaF gene resulted in expression of both wild-type LOS and wild-type virulence by this mutant.

Amino Acid Sequence↗

Analysis of aberrant DNA methylation and human papillomavirus DNA in cervicovaginal specimens to detect invasive cervical cancer and its precursors.

PURPOSE: Cancer of the uterine cervix is an important cause of death in women worldwide. Pap smears as a tool for screening decreased the incidence and mortality of cervical cancer dramatically. This proof of principle study aimed to develop a potential tool for cervical screening using a test that can be applied by patients without visiting a physician and to increase the coverage rate, especially of the high-risk population with low socioeconomic status. EXPERIMENTAL DESIGN: Human papillomavirus (HPV) DNA testing and methylation analysis of DNA obtained from cervicovaginal specimens of 13, 31, and 11 patients with no dysplasia/low-grade squamous intraepithelial lesion (SIL), high-grade SIL, and invasive cervical cancer, respectively, collected on a tampon, was performed using PCR-based methods to detect invasive cervical cancer and study whether these changes are already present in the precursor lesions. RESULTS: High-risk HPV DNA was present in 68 and 82% of patients with high-grade SIL and invasive cervical cancer. DNA methylation of the 11 genes tested increased with severity of the cervical lesion. Unsupervised hierarchical cluster analysis using solely information on DNA methylation of the 11 genes was able to predict the presence of invasive cervical cancers: one of the two clusters formed contained 9 of 11 invasive cervical cancers, as well as two high-grade SILs. CONCLUSIONS: HPV DNA and DNA methylation analyzed in cervicovaginal specimens are able to predict invasive cervical cancers. To detect all high-grade SILs when applying this test, genes that become methylated earlier throughout cervical carcinogenesis have to be defined.

DNA↗

Transforming activity of the RL-akt gene, a c-akt gene activated by long terminal repeat insertion in murine leukemia RL(male symbol)1 cells.

The unique antigen peptide pRL1 on BALB/c radiation-induced leukemia RL(male symbol)1 cells is derived from the normally untranslated 5' region of the mouse c-akt gene. Insertion of an endogenous long terminal repeat into the first coding exon of the gene resulted in the enhanced production of an altered akt protein, RL-akt, and creation of the tumor rejection antigen peptide pRL1. In this study, we constructed an RL-akt-expressing vector to investigate the transforming ability and anti-apoptotic activity of RK-akt in NIH/3T3 cells. RL-akt-expressing clones formed more colonies than did c-akt-expressing clones in soft agar and exhibited increased saturation density, a lower serum requirement for growth, and tumorigenicity on athymic nude mice. Immunoblot analysis of subcellular protein distribution showed that a considerable proportion of RL-akt was distributed in the membrane fraction. Thus, RL-akt expressed in NIH/3T3 cells appeared to behave like the v-akt oncoprotein. Furthermore, the RL-akt gene conferred resistance to the apoptosis induced by the calcium ionophore A23187 and by ultraviolet irradiation of NIH/3T3 cells. These findings indicate that the RL-akt gene is able to transform cells and exerts an anti-apoptotic effect on recipient cells, thereby implicating the gene in leukemogenesis of RL(male symbol)1 cells.

3T3 Cells↗

E1A overcomes the apoptosis block in BCR-ABL+ leukemia cells and renders cells susceptible to induction of apoptosis by chemotherapeutic agents.

A crucial function of the BCR-ABL chimeric gene in chronic myeloid leukemia is the prolongation of cell survival by inhibition of apoptosis. BCR-ABL expression confers cross-resistance to multiple genotoxic anticancer drugs by inhibition of the apoptotic response to DNA damage in association with cell cycle arrest at the G2-M restriction point. Previous reports indicated that BCR-ABL exerts its antiapoptotic effect against various apoptotic stimuli upstream to the cleavage and activity of caspase-3. Here we show that the adenovirus E1A protein induces substantial apoptosis in BCR-ABL expressing K562 and LAMA-84 leukemia cells. This apoptotic activity of E1A is accompanied by processing of caspase-3 and cleavage of poly(ADP-ribose) polymerase and can be significantly blocked by z-VAD-fmk Z-Val-Ala-Asp(OCH3)-CH2F and the caspase-3-specific inhibitor Z-DEVD-FMK Z-Asp(OCH3)-Glu-Val-Asp(OCH3)-CH2F. Moreover, E1A renders K562 cells, which are particularly resistant to cell death irrespective of the inducing agent, susceptible to induction of apoptosis by the chemotherapeutic agents etoposide and daunorubicin. Counteracting the DNA damage-induced inactivation of cdc2 kinase, E1A reverses the drug-induced G2-M arrest These results indicate that solitary delivery of E1A significantly antagonizes BCR-ABL-induced antiapoptotic functions and circumvents the inherent resistance to DNA damage-induced apoptosis, supporting the use of E1A in combination with chemotherapeutic agents as a promising therapeutic strategy for successful treatment of Philadelphia chromosome-positive leukemia in vivo.

Adenovirus E1A Proteins↗

Biochemical and genetic analyses of ferulic acid catabolism in Pseudomonas sp. Strain HR199.

The gene loci fcs, encoding feruloyl coenzyme A (feruloyl-CoA) synthetase, ech, encoding enoyl-CoA hydratase/aldolase, and aat, encoding beta-ketothiolase, which are involved in the catabolism of ferulic acid and eugenol in Pseudomonas sp. strain HR199 (DSM7063), were localized on a DNA region covered by two EcoRI fragments (E230 and E94), which were recently cloned from a Pseudomonas sp. strain HR199 genomic library in the cosmid pVK100. The nucleotide sequences of parts of fragments E230 and E94 were determined, revealing the arrangement of the aforementioned genes. To confirm the function of the structural genes fcs and ech, they were cloned and expressed in Escherichia coli. Recombinant strains harboring both genes were able to transform ferulic acid to vanillin. The feruloyl-CoA synthetase and enoyl-CoA hydratase/aldolase activities of the fcs and ech gene products, respectively, were confirmed by photometric assays and by high-pressure liquid chromatography analysis. To prove the essential involvement of the fcs, ech, and aat genes in the catabolism of ferulic acid and eugenol in Pseudomonas sp. strain HR199, these genes were inactivated separately by the insertion of omega elements. The corresponding mutants Pseudomonas sp. strain HRfcsOmegaGm and Pseudomonas sp. strain HRechOmegaKm were not able to grow on ferulic acid or on eugenol, whereas the mutant Pseudomonas sp. strain HRaatOmegaKm exhibited a ferulic acid- and eugenol-positive phenotype like the wild type. In conclusion, the degradation pathway of eugenol via ferulic acid and the necessity of the activation of ferulic acid to the corresponding CoA ester was confirmed. The aat gene product was shown not to be involved in this catabolism, thus excluding a beta-oxidation analogous degradation pathway for ferulic acid. Moreover, the function of the ech gene product as an enoyl-CoA hydratase/aldolase suggests that ferulic acid degradation in Pseudomonas sp. strain HR199 proceeds via a similar pathway to that recently described for Pseudomonas fluorescens AN103.

Acetyl-CoA C-Acyltransferase↗

Selective enhancing effect of the Yaa gene on immune responses against self and foreign antigens.

The BXSB Y chromosome-linked mutant gene, Yaa, accelerates the progression of a lupus-like autoimmune syndrome only in mice that are predisposed to autoimmune diseases. Unlike the lpr gene, which causes the defects in the Fas antigen-mediating apoptosis, the autoimmune enhancing activity of the Yaa gene is selective, depending on autoantigens, and varies among lupus-prone mice. To obtain a better definition of the role of the Yaa gene in the acceleration of autoimmune disease, we have investigated immune responses to several foreign antigens to determine whether the Yaa gene is able to potentiate immune responses to foreign antigens in a selective manner. We report here that the Yaa gene potentiated immune responses against foreign antigens only in mice which are genetically (H-2-linked) low responding, but not high or non-responding. Moreover, studies on Yaa(+)-Yaa- double bone marrow chimeric mice revealed that B cells from Yaa+ mice were selectively stimulated to produce antibodies to low-responding antigen, human IgG, while both B cell populations similarly responded to high-responding antigen, ovalbumin. Our results suggest that first, the selective immune enhancing activity of the Yaa gene may be related to differences in the capacity of T helper cells specific for given self or foreign antigens; and second, a specific cognate interaction of T helper cells with Yaa+ B cells is apparently responsible for the selective enhancement of immune responses to antigens, to which mice are genetically low responding.

Animals↗

Studies of some mechanisms of drug resistance in chronic myeloid leukemia (CML).

CML is the myeloproliferative disorder connected with the specific chromosome translocation (9;22) and occurrence of the fusion gene/protein BCR-ABL. BCR-ABL protein is believed to inhibit apoptosis and to cause drug resistance. We investigated the correlation of two different forms of BCR-ABL mRNA in 94 pts with their overall survival. It was found that b2a2 (but not b2a3) mRNA expression correlates with longer survival of patients treated with chemotherapy. We did not find an influence of different types of BCR/ABL mRNA on the survival of pts treated with interferon-alpha. FAS/APO-1 antigen was expressed by the cells of 34% of the pts in CML blast crisis (BC) and directly correlated with the the expression of CD34, CD13 and CD14 differentiation antigens. FAS/APO-1 non-expression correlated with higher rate of remissions in BC. We investigated P-glyco-protein (Pgp) expression and functional activity in 40 BC CML pts. 2-fold shorter survival was found in the pts with Pgp expression. Pgp expression strongly correlated with CD13 antigen. Consecutive studies of pts in BC CML show that Pgp expressing cells often do not multiply in the course of BC CML. We postulate that Pgp may be regarded as differentiation marker of the cells and the unfavorable prognostic factor in BC CML.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Preliminary study on bcr rearrangement in leukemia.

Southern blot analysis was conducted in 15 patients by using a 1.2 Kb Hind III/Bgl II fragment from the 3' end of the bcr region and a 2.0 Kb Bgl II/Hind III fragment from the 5' end of the bcr as probes. Of the 15 patients in our group, 11 with chronic, myelocytic leukemia (CML), 3 with Ph-negative acute lymphocytic leukemia (ALL), one with myelodysplastic syndrome (MDS). Bcr rearrangements were detected in 9 patients with CML and were negative in the rest of the patients. The results showed that the identification of bcr rearrangement was very important in the diagnosis of Ph-positive leukemias.

Adolescent↗

Osteopontin is upregulated by BCR-ABL.

Chronic myelogenous leukemia (CML) is characterized by its hallmark oncogene BCR-ABL and the progression from a chronic phase toward an acute leukemia, with a differentiation arrest of the leukemic clone. In the present study, we conducted a microarray analysis using an inducible model of BCR-ABL expression based on the TET-OFF system, and we found that osteopontin (OPN), a component of stem cell niche, is overexpressed in BCR-ABL-expressing cells. Studies using mutant forms of BCR-ABL demonstrated that the BCR-ABL-induced OPN overexpression was a tyrosine kinase-dependent event. Furthermore, OPN concentration was significantly increased in the serum of leukemic mice generated by transplantation of BCR-ABL-expressing bone marrow cells. Most importantly, a significant increase of OPN concentration was observed in the serum of CML patients as compared to controls. Overall these results show that OPN is deregulated by BCR-ABL oncogene and suggest that OPN could be involved in CML stem cell biology.

Animals↗

A novel BCR-ABL rearrangement in a Philadelphia chromosome-positive chronic myelogenous leukaemia variant with thrombocythaemia.

Reverse transcription polymerase chain reaction was used to detect an unusual BCR/ABL transcript in a patient who presented with thrombocythaemia and was Philadelphia chromosome positive but weakly reactive to conventional BCR/ABL fusion probes. Sequencing revealed the presence of a 12 bp insert between BCR exon2 (b2) and ABL exon2 (a2). In such cases the use of conventional BCR/ABL probes may lead to false negative results. This is the first report of this transcript. Clinically the patient has responded well to therapy.

Adult↗

Mutator phenotype of BCR--ABL transfected Ba/F3 cell lines and its association with enhanced expression of DNA polymerase beta.

Chronic myelogenous leukemia (CML) is characterized by the Philadelphia chromosome resulting from the translocation t(9-22) producing the chimeric 190 and 210 kDa BCR-ABL fusion proteins. Evolution of the CML to the more agressive acute myelogenous leukemia (AML) is accompanied by increased cellular proliferation and genomic instability at the cytogenetic level. We hypothezised that genomic instability at the nucleotide level and spontaneous error in DNA replication may also contribute to the evolution of CML to AML. Murine Ba/F3 cell line was transfected with the p190 and p210-encoding BCR-ABL oncogenes, and spontaneous mutation frequency at the Na-K-ATPase and the hypoxanthine guanine phosphoribosyl transferase (HPRT) loci were measured. A significant 3-5-fold increase in mutation frequency for the transfected cells relative to the untransfected control cells was found. Furthermore, we observed that BCR-ABL transfection induced an overexpression of DNA polymerase beta, the most inaccurate of the mammalian DNA polymerases, as well as an increase in its activity, suggesting that inaccuracy of DNA replication may account for the observed mutator phenotype. These data suggest that the Philadelphia abnormality confers a mutator phenotype and may have implications for the potential role of DNA polymerase beta in this process.

Animals↗