Isolation and characterization of nonhistone proteins associated with DNase-II hypersensitive sites of Sarcoma-180 chromatin.

Limited digestion (2 min) of Sarcoma-180 nuclei by DNase-II released two nonhistone proteins from the hypersensitive sites of chromatin. The apparent molecular weights of these two proteins were 34 and 21 kDa. These proteins showed a moderate but specific inhibition in in vitro cell free transcription assay with native chromatin as template as opposed to no effect on native DNA transcription.

Effect of anthracycline antibiotics on in vitro transcription of chromatin in a Sarcoma-180 whole cell extract.

A soluble extract capable of transcribing Sarcoma-180 chromatin and DNA in a cell-free transcription system was prepared from Sarcoma-180 mouse ascites tumour cells. Incorporation of [3H]UTP into trichloroacetic acid-precipitable fraction is (i) reduced by 50% on removing DNase I hypersensitive sites of chromatin and (ii) inhibited by DNA binding antitumour anthracyclines, suggesting that this cell-free assay represents true transcription of active genes of Sarcoma-180 chromatin. Preparation of this soluble extract from mouse ascites tumour cells thus presents a very convenient way of studying cell-free transcription of active genes of chromatin and effect of antitumour agents on chromatin transcription.