Alterations in chromatin of cells infected with RNA tumor viruses.

Chromatins were isolated from murine leukemia or sarcoma virus infected lymphocyte-like TB cells and compared by immunological and biochemical methods. Chromatin from virus infected cells did not fix complement as well as uninfected cell chromatin suggesting that conformational changes had occurred in chromatin from virus infected cells. This alteration was detected within 24 hours after infection. Infected cell chromatins, examined by electrophoretic methods after radiolabeling displayed alterations in nonhistone proteins, whereas the histones appeared unaltered. The non-histones were synthesized in greater amounts in infected compared to normal cells, particularly a 60,000 D protein, while the amount of histone did not vary. The above changes should not have been due to cell growth or cycle variations, for the cells had similar growth rates and were harvested from the same stage of cell confluency during exponential growth to ensure uniformity of culture conditions.