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G Chinnadurai

Publications and source records attributed to G Chinnadurai.

103 records · Page 6Linked to original sources
PubMed1979

A unique subgenomic species of adenovirus 2 DNA generated under high multiplicities of infection.

We have identified a novel subgenomic viral DNA in KB cells infected with adenovirus 2 (Ad2) under high multiplicities of infection. KB cells were infected with Ad2 at multiplicities of infection greater than 100 PFU/cell. 32P-labeled viral DNA was selectively extracted by a modification of the method of Hirt (8) from the infected cells and analyzed by electrophoresis on agarose gels. In addition to full-length DNA (33 to 23 x 10(6) daltons), a unique subgenomic DNA species of about 12 to 13% (2.6 x 10(6) daltons) of full-length DNA in size was found in the infected cells. This subgenomic DNA was found to be double stranded and was not packaged inside the virus particles. This DNA could be isolated in large amounts (30 to 50% of total viral DNA) from infected cells. When cleaved with restriction endonuclease KpnI, the subgenomic DNA yielded two fragments, each corresponding to about 6% and 7% of the full-length genome in size.

Adenoviruses, Human↗
PubMed1979

Physical mapping of a large-plaque mutation of adenovirus type 2.

We have developed a simple method based on cotransfection of overlapping DNA restriction fragments for construction of recombinants of adenovirus type 2 (Ad2) and Ad5. When Ad2 DNA digested with restriction endonuclease EcoRI was cotransfected with Ad5 DNA digested with SalI, recombination occurred between Ad2 EcoRI-A (map position 0 to 59) and Ad5 SalI-A (map position 45 to 100). Analysis of the recombinant DNAs by digestion with EcoRI or BamHI restriction endonucleases indicated that, as expected, recombination had occurred in overlapping sequences (map position 45 to 59) between the Ad2 EcoRI-A fragment and the Ad5 SalI-A fragment. By using this method, several recombinants were constructed between a large-plaque (lp) mutant of Ad2 and wild-type Ad5. Cleavage of the recombinant genomes with restriction endonucleases BamHI, EcoRI, and HindIII revealed that the lp mutation is located within the left 41% of Ad2 genome.

Adenoviruses, Human↗
PubMed1978

Enhanced infectivity of adenovirus type 2 DNA and a DNA-protein complex.

The infectivity of adenovirus type 2 DNA and a DNA-protein complex was studied in 293 cells, a human embryonic kidney cell line transformed by sheared adenovirus type 5 DNA, and in human KB cells. Adenovirus type 2 DNA was more infectious (up to about 40-fold) in 293 cells than in KB cells, whereas a DNA-protein complex (prepared by a rapid procedure) had about the same infectivity in both cell lines. These data may mean that a factor present in 293 cells (perhaps a viral-coded protein) enhances the infectivity of free viral DNA. The infectivity of DNA and the DNA-protein complex was increased up to fivefold by brief treatment of cell monolayers with 25% dimethyl sulfoxide after transfection. Under these conditions, (i) the infectivity of native adenovirus type 2 DNA ranged from 400 to 1,300 PFU/microgram of DNA in 293 cells and from about 9 to 14 PFU/microgram of DNA in KB cells, and (ii) the infectivity of the DNA-protein complex was 6 X 10(3)to 2 X 10(4) PFU/microgram in 293 cells and 1.4 X 10(4) to 1.6 X 10(4) PFU/microgram in KB cells.

Adenoviruses, Human↗
PubMed1977

Pre-early polypeptides of bacteriophages T5 and BF23.

Nine pre-early polypeptides have been detected after infection with bacteriophage T5 and 10 pre-early polypeptides have been detected after infection with bacteriophage BF23. Only about one-half of the coding capacity of the redundant ends of the phage DNA, which code for pre-early proteins, is needed for these 9 to 10 pre-early polypeptides. The direction of transcription of pre-early genes A1 and A2 has been established from the size of N-terminal polypeptide fragments induced by amber mutants and from the known intragenic loci of the amber mutations. Some pre-early functions appear to be nonessential, because a viable deletion mutant of BF23 fails to induce three and possibly four of the detectable pre-early polypeptides.

Coliphages↗
PubMed1976

A unique pattern of integrated viral genes in hamster cells transformed by highly oncogenic human adenovirus 12.

We have analyzed the viral DNA sequences persisting in HE C19, a clonal line of hamster embryo cells transformed in vitro by human adenovirus 12 (Ad 12), a member of highly oncogenic group A. Saturation-hybridization of in vitro labeled Ad 12 DNA (2-4 x 10(8) cpm/mug) with HE C19 DNA showed that 93-100% of viral DNA sequences are present in the transformed cell. Reassociation of Ad 12 32P-DNA in the presence of HE C19 DNA detected 8 viral genome equivalents per diploid quantity of cell DNA. REannealing each of the six Ad 12 EcoRl restriction DNA fragments with HE C19 DNA indicated that the sequences of each fragment are present in near equimolar quantities, 8-10.5 copies per cell. HE C19 DNA "networks" were prepared and shown to contain the same viral DNA sequences and in the same amounts as present in unfractionated transformed cell DNA; these data provide the first direct evidence that human adenovirus genes are covalently linked to cellular DNA. The presence of most, if not all, of the viral genes was demonstrated also in the Ad 12 hamster tumor cell line, HT-2. The pattern of integrated viral genes in these nonpermissive hamster cells transformed by Ad 12 is different from that described for cells transformed by group C and B human adenoviruses and for SV40.

Adenoviridae↗
PubMed1976

mRNA from the transforming segment of the adenovirus 2 genome in productively infected and transformed cells.

We have identified two mRNA species transcribed from the adenovirus 2 genome section (HindIII-G fragment) believed to harbor genes for initiation and maintenance of cell transformation. The HindIII-G fragment occupies the left 7.5% of the genome and is transcribed from left to right [poly(U:G) r strand]. Poly(A)-terminated labeled mRNA was isolated from polyribosomes of adenovirus 2 early infected KB cells and from the transformed cell line 8617, hybridization purified using the HindIII-G fragment, and electrophoresed on formamide-polyacrylamide gels. Viral mRNA's of 24S (1.2 X 10(6) daltons) and 14S (4.5 X 10(5) daltons) were isolated from early infected cells and of 22S (1.0 X 10(6) daltons) and 14S from 8617 cells. Hybridization competition indicated that HindIII-G-specific mRNA was present in the polysomes at one-sixth the concentration late after infection as compared with early, indicating that the proteins coded by the transforming segment may be synthesized at reduced amounts during late stages. Only 1/10 the amount of RNA labeled late annealed to the G fragment as compared with that labeled early (per weight of RNA). Thus, synthesis of transforming gene mRNA is probably "turned off" late after infection. Both 24S (22S) and 14S mRNA's from infected and 8617 cells were complementary to the Hpa I-E fragment (left 4.1% of genome). The Hpa I-E fragment is too small to encode 24S and 14S species, which implies that the 5'-terminal regions of both species are coded by the same DNA sequences.

Adenoviruses, Human↗
PubMed1974

Regulation of expression of late genes of bacteriophage T5.

Amber mutants of bacteriophage T5 defective in gene C2 have been characterized. The product of this gene is required for the normal turn-on of synthesis of late RNA's and proteins, and, apparently, for the normal continued synthesis of early RNA's and proteins during late stages of infection. The inability of nonpermissive cells to synthesize any proteins, either late or early, during the late period after infection with a C2-mutant is not due to premature lysis of the infected cells, to a depletion of the cellular energy supply, or to degradation of phage DNA at late times. A possible role for the product of gene C2 in early and late transcription of the viral genome is suggested.

Autoradiography↗
PubMed1973

Requirement of a phage-induced 5'-exonuclease for the expression of late genes of bacteriophage T5.

Amber mutants of bacteriophage T5 defective in gene D15, which codes for a 5'-exonuclease, do not express late genes. Electrophoretic separation in sodium dodecyl sulfate-polyacrylamide gels of the proteins induced by this mutant in nonpermissive Escherichia coli show a virtual absence of late proteins. Synthesis of lysozyme and serum-blocking power is very low whereas the extent of synthesis of an early enzyme, deoxyribonucleoside monophosphokinase, is similar to that in wild-type infections. It is proposed that one requirement for the expression of late T5 genes is the introduction of gaps or nicks in the T5 DNA so that late transcription can occur.

Carbon Radioisotopes↗