Single-stranded DNA from oncornavirus-infected cells enriched in virus-specific DNA sequences.

We previously found that a minor fraction of single-stranded DNA (ss-DNA) isolated from native nuclear DNA of normal chicken embryonic cells and cells of other species hybridized with bulk nuclear DNA or cellular RNA in great excess. At least one-third of ss-DNA belonging to the nonrepetitious part of the cell genome could be hybridized to homologous RNAs. In the present work, similar results were obtained with ss-DNA from cells of chickens infected by avian myeloblastosis virus (AMV).

Isolation of single stranded transcription sites from human nuclear DNA.

Single stranded DNA (ss-DNA) isolated from nuclear DNA of human rhabdomyosarcoma (RD line) cells amounts to 2% of total DNA. As compared with native double-stranded DNA (ds-DNA), ss-DNA has a lower mean sedimentation coefficient, higher buoyant density, contains fewer repeated DNA sequences and a greater proportion of it can be hybridized to human RNAs (up to 35% and less than 8% for ds-DNA). The hybridization kinetics determined by S1 nuclease digestion and verified by other methods (hydroxylapatite chromatography, density gradient centrifugation and thermal melting) indicate that ss-DNA corresponds to a great number and variety of transcripts.

Isolation of single stranded DNA related to the transcriptional activity of animal cells.

Single stranded DNA (s.s.DNA) comprising 1-2% of the total nuclear DNA was isolated by an improved method of hydroxyapatite chromatography from native nuclear DNA3 of embryonic chick cells, labeled for several cell generations with 3H-thymidine.

Polyadenylation of ribonucleic acids in mouse L cells infected by encephalomyocarditis virus.

Polyadenylation of cytoplasmic RNAs was investigated in L cells infected with encephalomyocarditis virus. During the early stage of infection, the mean size of newly made poly(A) chains attached to cell mRNAs decreased gradually, in parallel with the shut-off of RNA synthesis. Later on, poly(A) segments, an average of 50 nucleotides long, were associated with viral RNA isolated either from polysomes or whole cytoplasm.

[Demonstration of repeated sequences of DNA complementary to polysomic messenger RNA from chicken liver].

Radioactive nuclear DNA from chicken cells was fractionated according to their frequency of reiteration. By hybridization with an excess of purified polysomal mRNA, the proportion of repetitious DNA hybridized, greatly exceeded that of non-repetitious DNA.

Distribution of repetitious sequences in chick nuclear DNA.

By an improved method of hydroxylapatite chromatography, the reassociated sequences of chick nuclear DNA were isolated, and their base composition analysed. By increasing the amount of reassociation, the G + C content of the renatured sequences decreased progressively to reach a mean value corresponding to that of the total DNA. In order to study the distribution of the families, or group of families having different amount of reassociation, DNA was fractionated by CsC1 density gradient centrifugation.