DNA base sequence variability in katF (putative sigma factor) gene of Escherichia coli.
Explore the source record for details and available documents.
Amino Acid Sequence↗
Biomedical subjects
R V Guntaka
Publications and source records attributed to R V Guntaka.
Involvement of tyrosine kinase and protein kinase C in platelet-activating-factor-induced c-fos gene expression in A-431 cells.
In A-431 cells, platelet-activating factor (PAF) induces the expression of c-fos and TIS-1 genes in both the absence and the presence of cycloheximide in a structurally specific and receptor-coupled manner. We have now investigated the molecular mechanisms of this response, particularly in relation to the role of protein kinases. Pretreatment of cells with genistein or methyl-2,5-dihydroxycinnamate (tyrosine kinase inhibitors) or staurosporine (a protein kinase C inhibitor) for 20 min abolished the c-fos expression induced by PAF. Interestingly, when genistein was added 90 s after addition of PAF, no inhibition was observed. Similarly, staurosporine did not inhibit c-fos expression when added 8 min after PAF addition to the cells. These inhibitions were dose-dependent (IC50 for staurosporine was 180 nM, and for genistein 50 microM). Simultaneous addition of PAF and phorbol 12-myristate 13-acetate (PMA) did not give a synergistic effect on c-fos expression. Pretreatment of cells with PMA had no effect on [3H]PAF binding, but abolished the PAF-induced gene expression. PAF-stimulated gene expression was desensitized if cells were pretreated with PAF. Interestingly, epidermal growth factor was able to stimulate c-fos expression in PAF-desensitized cells, and thus indicated involvement of distinct mechanisms for the two stimuli. Forskolin, an activator of adenylate cyclase, did not induce c-fos expression and had no effect on the PAF response. Exposure of cells to PAF for as little as 1 min, followed by its removal, was sufficient to activate the gene expression and demonstrated the rapidity and the exquisite nature of the signalling involved in this process. It is concluded that activation of PAF receptor (a proposed G-protein-coupled receptor) causes rapid production of signals which induce the expression of c-fos gene and that this is mediated via tyrosine kinase and protein kinase C.
Alkaloids↗
Cloning and characterization of a highly conserved HMG-like protein (PF16) gene from Plasmodium falciparum.
A novel gene encoding a protein of 147 amino acids (Pf16) has been cloned from Plasmodium falciparum and expressed in E. coli. The protein contains 19 methionines, all of which are localized in the NH2-terminal 35 amino acid residues, and it is also rich in lysine. Pf16 is highly basic, contains a polyacidic domain consisting of aspartic acid and is related to the non-histone high mobility group proteins of higher eukaryotes. The gene is conserved among eight different species of Plasmodium so far examined, suggesting an important function for this gene product in the parasite's life cycle.
Amino Acid Sequence↗
Tumor induction by the LTR, v-src, LTR DNA in four B (MHC) congenic lines of chickens.
We report that the cloned DNA harboring the long terminal repeat (LTR), v-src, LTR proviral structure is tumorigenic in chickens of the Prague congenic lines. The growth rate of these tumors is by far the highest in the recombinant CC.R1 line, the B haplotype of which is composed of the B-F/L4 and B-G12 subregions originating from different naturally occurring haplotypes. Some of the tumors induced by the LTR, v-src, LTR DNA are repeatedly transplantable in syngeneic chickens, maintain unaltered provirus, and express v-src mRNA. Differences in the response to challenge with Rous sarcoma virus (RSV) and LTR, v-src, LTR DNA on a given experimental model are compared and possible involvement of an interaction between B-F/L and B-G region genes is considered. Regression of the LTR, v-src, LTR DNA-induced tumors did not prevent the formation and growth of tumors induced subsequently by RSV.
Animals↗
Improved method for screening cDNA expression libraries for DNA-binding proteins.
The ability to successfully screen a lambda gt11 cDNA expression library for specific gene products that can bind to selected sequences of DNA depends on radioactive double-stranded DNA probes with high specific activity. We demonstrate here that probes labeled by the PCR are superior to probes made by the Klenow reaction. The use of these PCR-generated probes have facilitated our efforts to isolate recombinant phage containing putative DNA-binding gene products that recognized a 246-base pair transcriptional enhancer region of Rous sarcoma virus long terminal repeat.
Animals↗
Platelet activating factor induces expression of early response genes c-fos and TIS-1 in human epidermoid carcinoma A-431 cells.
The effect of platelet activating factor (PAF) on the induction of early response genes was investigated in A-431 cells (human epidermal carcinoma cells). PAF induced a transient expression of c-fos and TIS-1 mRNA in a time- and dose-dependent manner. As low as 10(-10) M PAF caused detectable expression of these genes with a maximum observed at 10(-7) M. In the presence of cycloheximide, increases in the gene expression were noticeable at 20 min and peaked between 30-60 min. A lack of induction with lyso-PAF, an inactive PAF metabolite, confirmed the specificity of PAF towards this expression. The cells pretreated with CV-6209, a PAF receptor antagonist, did not show any induction of these genes by PAF. It is concluded that PAF causes induction of the early response genes c-fos and TIS-1 in a structurally specific and receptor dependent manner. This finding offers a new role for PAF at the nuclear level and may have important implications in the long term effects of PAF in pathophysiological conditions.
Cycloheximide↗
2-Chloroacetaldehyde and 2-chloroacetal are potent inhibitors of DNA synthesis in animal cells.
The effect of 2-chloroacetaldehyde, CAA, a metabolite of vinyl chloride and 2-chloroacetal, CAC, an ethyl diester of chloroacetaldehyde, on DNA synthesis in animal cells has been investigated. Both compounds drastically inhibited DNA synthesis at 10 to 20 microM. The inhibitory effect of the chemicals appears to be directly on DNA synthesis rather than on the uptake of thymidine or the formation of nucleotides. Residual DNA made in the presence of CAA had an average chain length of 300 nucleotides compared to a length of several thousand nucleotides in the absence of CAA. Synchronization experiments revealed that the inhibitory effect is reversible if 2-chloroacetaldehyde is removed within two hours but not after longer exposures.
Acetaldehyde↗
Localization by mutational analysis of transcription factor binding sequences in the U3 region of Rous sarcoma virus LTR.
The transcription factor binding sequences in the U3 region of Rous Sarcoma virus LTR have been determined by gel retardation assays using mutant synthetic oligonucleotides. The results indicate that the factor, E2BP, specifically binds to sequences TGCAATAC and TGCAACAT, which are localized between nucleotides -222 to -215 and -203 to -196, respectively. This factor is present at elevated levels in avian QT6 cells compared to mouse 3T3 and rat 2 tk- cells. E2BP binds to a sequence that is similar or identical to the sequence recognized by rat liver C/EBP. However, the two proteins are different as judged by three criteria: (i) the E2BP complex migrates slightly faster than the E2-C/EBP complex; (ii) antibodies against C/EBP neither inhibit binding of E2BP nor form a supercomplex which migrates slower than the complex formed with the factor alone; and (iii) E2BP is heat labile whereas C/EBP is heat stable. Another factor, E3BP, which binds to a sequence from -169 to -158, in the U3 region is also detected mainly in QT6 cells but not in mouse or rat cells. These results suggest that different cell-specific factors interact with different cis-acting regulatory sequences in the U3 region of RSV LTR.
Animals↗
A transformation-competent recombinant between v-src and Rous-associated virus RAV-1.
The LTR, v-src, LTR provirus, which arose by the reverse transcription and integration of src mRNA in the H-19 hamster tumor, has been successfully rescued by fusion with chicken fibroblasts infected with Rous-associated virus RAV-1. One rescued virus, E6, acquired 1 kilobase of the 5' end of the gag gene structure. Recombination took place in the region of 15-nucleotide homology exactly between v-src exon (position 7054) and gag (position 1417). This recombination resulted in the alteration of src splice acceptor site sequences, but this site is maintained as a functional splice acceptor site. The nucleotide structure of the long terminal repeat of recombinant E6 virus suggests that it arose by the intermolecular jump of reverse transcription from RAV-1 to src mRNA and then the switch of templates between already depicted regions of homology. The second jump of reverse transcription was apparently an intramolecular event. The acquisition of 1 kilobase of the 5' gag by E6 resulted in maintaining the balance of unspliced and spliced E6 RNAs and assured the replication advantage of rescued E6 virus over rescued F6 virus, the genome of which corresponds to that present in ancestral H-19 cells.
Animals↗
Identification of sequences in the long terminal repeat of avian sarcoma virus required for efficient transcription.
Two different vectors, LTR-NEO-LTR and LTR-CAT-LTR, were constructed and deletions were introduced in the upstream LTR at -299 and at -140. These deletion mutants were introduced into QT6 cells under transient expression conditions, and the levels of transcription were monitored by dot blot hybridization or by CAT assays. The results indicate that the nucleotides between -208 and -201 and between -141 and -119 in the U3 region of RSV LTR are required for efficient transcription.
Avian Sarcoma Viruses↗
Methylation of the enhancer region of avian sarcoma virus long terminal repeat suppresses transcription.
The effect of methylation of an enhancer on transcription was studied. A 245 bp enhancer-containing a fragment of the LTR of the avian sarcoma virus was methylated in vitro and ligated back into a vector which lacked the upstream enhancer sequence. The transient expression in QT6 cells indicated that methylation of the enhancer-containing sequence severely reduced the extent of transcription.
Avian Sarcoma Viruses↗
Organization of Plasmodium falciparum genome: II. Sequence analysis of falci element.
Explore the source record for details and available documents.
Plasmodium falciparum↗
Specific detection of Plasmodium falciparum malaria by a molecularly cloned DNA probe.
A highly repeated DNA sequence from Plasmodium falciparum was cloned and used as a probe in molecular hybridization to detect malaria. Our results indicate that the probe is specific to P. falciparum but not to other species of Plasmodium and is extremely sensitive. As little as a 20 pg parasite DNA, which is equivalent to about 1000 parasites can be detected. The cloned DNA can be used as a diagnostic tool to follow the course of infection of falciparum malaria.
Animals↗
Characterization of transforming viruses rescued from a hamster tumour cell line harbouring the v-src gene flanked by long terminal repeats.
The organization of proviruses derived from infecting transforming viruses rescued from hamster tumour cells was studied. Southern blot analysis indicated that the provirus from the F6 cell line was organized as long terminal repeat (LTR)-src-LTR, and S1 mapping experiments suggested that it was probably derived by reverse transcription of src mRNA followed by integration. In the E6 cell line, the provirus unit was arranged as LTR-delta gag-src-LTR, indicating a recombination event between the rescued transforming virus and the helper virus. These results suggest that transforming defective viruses containing only the src gene can be rescued from nonpermissive mammalian cells.
Animals↗
Organization of Plasmodium falciparum genome: 1. Evidence for a highly repeated DNA sequence.
Plasmodium falciparum DNA, isolated from the merozoite stage, was cleaved with HindIII and cloned in pBR322 and lambda L47.1 vectors. Plasmid clones containing 13.4, 7.0, 4.3, 4.1 and 1.5 kb inserts were characterized in some detail. The inserts contain several repeating units of smaller size. Nucleic acid hybridization studies showed that the repeat element is present in the Plasmodium DNA at a very high copy number and appears to be distributed widely throughout the genome.
Animals↗
Translation of avian sarcoma virus RNA in Xenopus laevis oocytes.
Explore the source record for details and available documents.
Animals↗
Avian RNA tumor virus DNA before and after integration into the host genome.
Explore the source record for details and available documents.
Animals↗
Effect of 5-methylcytidine on virus production in avian sarcoma virus-infected chicken embryo cells.
5-Methylcytidine (5mC) is a minor constituent of RNA in procaryotes as well as eucaryotes. The function of this modified nucleoside is not known. We studied the effect of this compound on virus production in avian sarcoma virus-infected chicken embryo fibroblasts. We found, surprisingly, that virus release into the medium was severely reduced in cultures treated with 5mC. In contrast to the effect of 5mC on virus release, intracellular levels of virus-specific RNA transcripts as well as the proteins were slightly elevated. Analysis of intracellular RNA transcripts on velocity gradients and virus-specific proteins in polyacrylamide gels did not reveal any qualitative differences in 5mC-treated cells compared to cytidine-treated cells. From these results we conclude that the effect of 5mC is probably at the level of virus maturation or packaging.
Animals↗