Search PubMed⌕ Search

Biomedical subjects

S J Flint

Publications and source records attributed to S J Flint.

80 records · Page 5Linked to original sources
PubMed1976

Adenovirus transcription. IV. Synthesis of viral-specific RNA in human cells infected with temperature-sensitive mutants of adenovirus 5.

Cytoplasmic RNA sequences produced in HeLa cells infected with the adeno-virus 5 temperature-sensitive mutants ts1, ts2, ts9, ts17, ts18, ts19, ts20, ts22, ts49, ts36, and ts125 were characterized by hybridization to DNA probes generated by strand separation of restriction endonuclease fragments of adenovirus 5 DNA. Two ""early'' mutants defective in DNA synthesis, ts125 and ts36, fail to make wild-type levels of all previously reported classes of late RNA at the nonpermissive temperature. At 40.5 degrees C, both ts125 and ts36 synthesize a wild-type complement of early cytoplasmic RNA 16 h after infection. Under these conditions, no ""late'' cytoplasmic RNA sequences were observed. Similarly, nuclear RNA present in these cells resembled early cytoplasmic RNA rather than late nuclear RNA. All the late adenovirus 5 temperature-sensitive mutants synthesized normal wild-type levels of late cytoplasmic RNA at the nonpermissive temperature, except ts2, which appears to overproduce certain cytoplasmic species.

Base Sequence↗
PubMed1975

Mapping of adenovirus 2 RNA sequences in lytically infected cells and transformed cell lines.

The strands of the six EcoRI fragments and the HpaI fragments E and C of Ad2 DNA were separated by electrophoresis in agarose gels. Using 32P-labeled fragment strands in solution hybridization experiments, the fraction of each strand complementary to RNA extracted from infected or transformed cells was assayed by chromatography on hydroxylapatite. In this manner, a tentative map of the cytoplasmic RNA sequences has been constructed for viral RNA extracted from cells both early and late during infection (see Fig. 16; in the map shown, the two strands of Ad2 are named the r and l strands following the bacteriophage convention). Since early cytoplasmic RNA anneals to four distinct regions of the genome, Ad2 probably codes for at least four early gene functions. Summation experiments have shown that all RNA sequences found in the cytoplasm of cells early during infection are also present in the cells' cytoplasm at late times. Viral RNA sequences in five independently isolated and cloned transformed rat cell lines were also mapped on the Ad2 genome. One class of Ad2-transformed rat cells contains RNA sequences complementary to only the segment of Ad2 DNA from 0.03-0.10 on the physical map, and this corresponds to one of the four regions of the genome expressed early during infection. If a viral gene product is necessary to maintain the transformed phenotype of the cell or codes for the virus-specific tumor (T) antigen, this genetic information must be at the left end of the genome (see Fig. 16). The two other classes of Ad2-transformed rat cells contain viral RNA sequences complementary to two or three of the regions of the genome transcribed into early cytoplasmic RNA. At both early and late times during the lytic cycle, the nucleus of the infected cell contains viral RNA sequences that are not transported to the cell's cytoplasm, suggesting that RNA processing and selection may play a role in the regulation of viral mRNA production.

Adenoviridae↗
PubMed1975

Adenovirus transcription. II. RNA sequences complementary to simian virus 40 and adenovirus 2DNA in AD2+ND1- and AD2+ND3-infected cells.

The genomes of the two nondefective adenovirus 2/simian virus 40 (Ad2/SV 40) hybrid viruses, nondefective Ad2/SV 40 hybrid virus 1 (Ad2+ND1) and nondefective hybrid virus 3 (Ad2+ND3), WERE FORMED BY A DELETION OF ABOUT 5% OF Ad2 DNA and insertion of part of the SV40 genome. We have compared the cytoplasmic RNA synthesized during both the early and late stages of lytic infection of human cells by these hybrid viruses to that expressed in Ad2-infected and SV40-infected cells. Separated strands of the six fragments of 32P-labeled Ad2 DNA produced by cleavage with the restriction endonuclease EcoRI (isolated from Escherichia coli) and the four fragments of 32P-labeled SV40 DNA produced by cleavage with both a restriction nuclease isolated from Haemophilus parainfluenzae, Hpa1, and EcoRI were prepared by electrophoresis of denatured DNA in agarose gels. The fraction of each fragment strand expressed as cytoplasmic RNA was determined by annealing fragmented 32P-labeled strands to an excess of cellular RNA extracted from infected cells. The segment of Ad2 DNA deleted from both hybrid virus genomes is transcribed into cytoplasmic mRNA during the early phase of Ad2 infection. Hence, we suggest that Ad2 codes for at least one "early" gene product which is nonessential for virus growth in cell culture. In both early Ad2+ND1 and Ad2+ND3-infected cells, 1,000 bases of Ad2 DNA adjacent to the integrated SV40 sequences are expressed as cytoplasmic RNA but are not similarly expressed in early Ad2-infected cells. The 3' termini of this early hybrid virus RNA maps in the vicinity of 0.18 on the conventional SV40 map and probably terminates at the same position as early lytic SV40 cytoplasmic RNA. Therefore, the base sequence in this region of SV40 DNA specifies the 3' termini of early messenger RNA present in both hybrid virus and SV40-infected cells.

Adenoviridae↗