Dynamics of ATP-dependent chromatin assembly by ACF.
The assembly of DNA into chromatin is a critical step in the replication and repair of the eukaryotic genome. It has been known for nearly 20 years that chromatin assembly is an ATP-dependent process. ATP-dependent chromatin-assembly factor (ACF) uses the energy of ATP hydrolysis for the deposition of histones into periodic nucleosome arrays, and the ISWI subunit of ACF is an ATPase that is related to helicases. Here we show that ACF becomes committed to the DNA template upon initiation of chromatin assembly. We also observed that ACF assembles nucleosomes in localized arrays, rather than randomly distributing them. By using a purified ACF-dependent system for chromatin assembly, we found that ACF hydrolyses about 2#150;4 molecules of ATP per base pair in the assembly of nucleosomes. This level of ATP hydrolysis is similar to that used by DNA helicases for the unwinding of DNA. These results suggest that a tracking mechanism exists in which ACF assembles chromatin as an ATP-driven DNA-translocating motor. Moreover, this proposed mechanism for ACF may be relevant to the function of other chromatin-remodelling factors that contain ISWI subunits.
Section of Molecular Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0347, USA.
Dmitry V
DV
Fyodorov
James T
JT
Kadonaga
D000255:Adenosine Triphosphate / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002843:Chromatin / Q000737:chemistry* / Q000378:metabolism*; D056504:Chromatin Assembly Factor-1; D002868:Chromosomal Proteins, Non-Histone; D004265:DNA Helicases / Q000378:metabolism; D004278:DNA, Superhelical / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006868:Hydrolysis; D008968:Molecular Conformation; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism; D021122:Protein Subunits; D011506:Proteins / Q000378:metabolism; D013698:Templates, Genetic; D013997:Time Factors
D018797:Cell Cycle Proteins; D002843:Chromatin; D056504:Chromatin Assembly Factor-1; D002868:Chromosomal Proteins, Non-Histone; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D006657:Histones; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D009707:Nucleosomes; D021122:Protein Subunits; D011506:Proteins; D000255:Adenosine Triphosphate; D004265:DNA Helicases