Facilitated transcription through the nucleosome at high ionic strength occurs via a histone octamer transfer mechanism.
The rate of transcription through the nucleosome, the fine structure of the nucleosomal barrier, and the fate of the nucleosome during transcription at different salt concentrations were analyzed using linear 227-base pair mononucleosomal templates containing a uniquely positioned nucleosome core. At lower ionic strength (30 mm NaCl), the nucleosome constitutes a strong barrier for SP6 RNA polymerase. At higher ionic strength (330 mm NaCl), the rates of transcription on nucleosomal and histone-free DNA templates are very similar. At both higher and lower ionic strengths, the complete histone octamer is transferred over the same distance by fundamentally similar mechanisms. The data indicate that even at the rate of transcription characteristic of histone-free DNA, the transfer intermediates can be formed quite efficiently. This suggests possible mechanisms that could facilitate transcription through the nucleosome at physiological ionic strength.
Walter
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Department of Biochemistry and Molecular Biology and Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Studitsky
V M
VM
D000818:Animals; D002645:Chickens; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D019281:Dimerization; D004912:Erythrocytes / Q000378:metabolism; D006657:Histones / Q000378:metabolism*; D008954:Models, Biological; D009707:Nucleosomes / Q000187:drug effects / Q000235:genetics*; D009994:Osmolar Concentration; D010957:Plasmids; D011401:Promoter Regions, Genetic; D021381:Protein Transport; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D013698:Templates, Genetic; D014158:Transcription, Genetic / Q000187:drug effects*
D006657:Histones; D009707:Nucleosomes; D012462:Saline Solution, Hypertonic; C070852:RNA polymerase SP6; D012321:DNA-Directed RNA Polymerases