The in vitro transcriptions from chromatins of Walker 256 carcinosarcoma, rat mammary gland, and rat liver were compared with respect to template activities and reciprocal double saturation hybridization of the transcribed RNA's. Walker tumor chromatin was found to have the least template activity in RNA synthesis in vitro, and the synthesized RNA, when annealed with DNA, also showed the least saturation hybridization plateau. Hybridization studies further showed the presence of new RNA species in transcripts from Walker tumor chromatin which were not detected in normal in vitro chromatin transcription. These results indicate that in the transformation from normal to neoplastic state both repression and derepression of normal transcribable DNA sequences occur.

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Supported by USPHS Grant GM-11698-08.

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