Stimulation of DNA polymerase alpha by a nuclear DNA/protein complex.

A nuclear DNA complex containing DNA polymerase and SV40 T-antigen was isolated from nuclei of SV40-transformed mouse fibroblasts. DNA polymerase could be separated from the complex. The remaining DNA/T-antigen-containing complex stimulated DNA polymerase alpha activity about 10-fold.

Retrovirus-like particles in EBV-negative Burkitt's lymphoma cell line but not in EBV-DNA-positive lines from patients with ataxia telangiectasia and Down's syndrome.

Retrovirus-like particles can be recovered by arginine deprivation from the BJAB-1 Epstein-Barr virus (EBV) negative cell line derived from an African patient with typical Burkitt's lymphoma. These particles resemble retroviruses in their morphology and in their physicochemical properties. Particles with a similar morphology were obtained from derivative cell lines established by infecting BJAB-1 cells with EBV.

Cytotoxic activity of methylene bis-nucleotides.

New facts relating to the mechanism of cytotoxic and antitumor activity of formaldehyde-treated RNA and its hydrolysates have been revealed. Synthetic methylene bis-nucleotides and, in particular, methylene bis-nucleosides have a cytotoxic effect on cultured human adenocarcinoma cells (line HCCL). The cytotoxic effect of methylene bis-derivatives of the guanine series was most pronounced.

Effect of hydrolyzed formaldehyde-treated RNA on neoplastic and normal human cells.

Alkaline hydrolysate of dialyzed formaldehyde-treated RNA, in which 39% of purine nucleotides are modified to methylene bis derivatives (R-CH2-R'), displays cytotoxic activity toward cultured human tumor cells. The alkaline hydrolysate of dialyzed formaldehyde-treated RNA is substantially less toxic to normal human embryonic cells. There is a correlation between the cytotoxic effect and cell growth rate, which has been traced by quantitative tests.