Nature Structural & Molecular Biology
- 13, 1078 - 1083 (2006)
Published online: 12 November 2006; | doi:10.1038/nsmb1170
The chromatin-remodeling enzyme ACF is an ATP-dependent DNA length sensor that regulates nucleosome spacingJanet G Yang1, 2, Tina Shahian Madrid1, 2, Elena Sevastopoulos1 & Geeta J Narlikar11
Department of Biochemistry and Biophysics, University of California, San Francisco, 600 16th Street, San Francisco, California 94158, USA. 2
These authors contributed equally to this work.
Correspondence should be addressed to Geeta J Narlikar gnarlikar@biochem.ucsf.edu Arrays of regularly spaced nucleosomes directly correlate with closed chromatin structures at silenced loci. The ATP-dependent chromatin-assembly factor (ACF) generates such arrays in vitro and is required for transcriptional silencing in vivo. A key unresolved question is how ACF 'measures' equal spacing between nucleosomes. We show that ACF senses flanking DNA length and transduces length information in an ATP-dependent manner to regulate the rate of nucleosome movement. Using fluorescence resonance energy transfer to follow nucleosome movement, we find that ACF can rapidly sample DNA on either side of a nucleosome and moves the longer flanking DNA across the nucleosome faster than the shorter flanking DNA. This generates a dynamic equilibrium in which nucleosomes having equal DNA on either side accumulate. Our results indicate that ACF generates the characteristic 50- to 60-base-pair internucleosomal spacing in silent chromatin by kinetically discriminating against shorter linker DNAs.
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