Actinomycin D binding in vitro: active chromatin preferred.
When [3H] Actinomycin D (Act. D) is used to interact with nuclei and nucleoli in vitro, it binds preferentially to nucleolar chromatin. The preferential binding is no longer detectable, when purified nuclear and nucleolar DNAs are used. In parallel, Act. D preferentially inhibits nucleolar over nuclear RNA synthesis when chromatin templates are used, and the preferential inhibition is lost when purified nuclear and nucleolar DNAs are used. It is concluded: 1) the preferential inhibition of nucleolar over nuclear RNA synthesis by Act. D is a direct reflection of the preferential binding of Act. D to the nucleolar chromatin; and 2) the nucleolar chromosomal proteins, not the nucleolar DNA, confer the preferential binding of Act. D.
Department of Biomedical Sciences, University of Illinois College of Medicine, Rockford 61107.
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D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D004247:DNA / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D003609:Dactinomycin / Q000378:metabolism*; D008099:Liver; D012313:RNA / Q000096:biosynthesis; D051381:Rats; D014158:Transcription, Genetic
D002843:Chromatin; D003609:Dactinomycin; D012313:RNA; D004247:DNA; D012321:DNA-Directed RNA Polymerases