The chromatin-remodeling enzyme ACF is an ATP-dependent DNA length sensor that regulates nucleosome spacing.
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.
Yang
Janet G
JG
Department of Biochemistry and Biophysics, University of California, San Francisco, 600 16th Street, San Francisco, California 94158, USA.
Madrid
Tina Shahian
TS
Sevastopoulos
Elena
E
Narlikar
Geeta J
GJ
D000255:Adenosine Triphosphate / Q000378:metabolism*; D002843:Chromatin / Q000235:genetics*; D056504:Chromatin Assembly Factor-1; D042002:Chromatin Assembly and Disassembly / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D009707:Nucleosomes / Q000235:genetics* / Q000378:metabolism
D002843:Chromatin; D056504:Chromatin Assembly Factor-1; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009707:Nucleosomes; D000255:Adenosine Triphosphate; D004247:DNA