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Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events
Published on: May 13, 2019
A histone octamer can step around a transcribing polymerase without leaving the template
V M Studitsky1, D J Clark, G Felsenfeld
1Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases National Institutes of Health Bethesda, Maryland 20892.
Cell
|January 28, 1994
Summary
Nucleosome cores move along DNA during transcription, stepping around the transcribing polymerase without dissociating. This translocation mechanism ensures gene expression regulation.
Area of Science:
- Molecular Biology
- Epigenetics
- Gene Regulation
Background:
- Nucleosomes are fundamental units of DNA packaging in eukaryotes.
- Understanding nucleosome dynamics during transcription is crucial for gene regulation.
- Previous models proposed various mechanisms for nucleosome displacement.
Purpose of the Study:
- To investigate the mechanism of nucleosome core displacement and reformation during in vitro transcription.
- To elucidate the role of DNA template length and nucleotide concentration on nucleosome movement.
- To provide evidence for a specific translocation model of nucleosome dynamics.
Main Methods:
- Assembly of nucleosome cores on defined DNA templates (227 bp and 262 bp) containing SP6 RNA polymerase promoter.
- In vitro transcription assays at varying concentrations of ribonucleotide triphosphates (rNTPs).
- Analysis of nucleosome core position relative to the promoter after transcription.
Main Results:
- Transcription induced nucleosome core translocation over 75-80 bp, blocking the promoter.
- Nucleosome transfer occurred intramolecularly at low rNTP concentrations.
- Nucleosome position on longer templates was dependent on its initial position.
- Data suggest octamer transfer without dissociation from DNA.
Conclusions:
- Strong evidence supports a DNA translocation mechanism for nucleosome repositioning during transcription.
- The nucleosome octamer "steps" around the transcribing polymerase.
- This mechanism allows for transcription while maintaining nucleosome integrity.
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