title: DNA translocation and loop formation mechanism of chromatin remodeling by SWI/SNF and RSC.
abstract: ATP-dependent chromatin-remodeling complexes (remodelers) modulate gene transcription by regulating the accessibility of highly packaged genomic DNA. However, the molecular mechanisms involved at the nucleosomal level in this process remain controversial. Here, we monitor the real-time activity of single ySWI/SNF or RSC complexes on single, stretched nucleosomal templates under tensions above 1 pN forces. We find that these remodelers can translocate along DNA at rates of approximately 13 bp/s and generate forces up to approximately 12 pN, producing DNA loops of a broad range of sizes (20-1200 bp, average approximately 100 bp) in a nucleosome-dependent manner. This nucleosome-specific activity differs significantly from that on bare DNA observed under low tensions and suggests a nucleosome-remodeling mechanism through intranucleosomal DNA loop formation. Such loop formation may provide a molecular basis for the biological functions of remodelers.
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Yongli
authors.initials: Y
authors.lastname: Zhang
authors.forename: Corey L
authors.initials: CL
authors.lastname: Smith
authors.forename: Anjanabha
authors.initials: A
authors.lastname: Saha
authors.forename: Stephan W
authors.initials: SW
authors.lastname: Grill
authors.forename: Shirley
authors.initials: S
authors.lastname: Mihardja
authors.forename: Steven B
authors.initials: SB
authors.lastname: Smith
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Cairns
authors.forename: Craig L
authors.initials: CL
authors.lastname: Peterson
authors.forename: Carlos
authors.initials: C
authors.lastname: Bustamante
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D002645:Chickens; D042002:Chromatin Assembly and Disassembly; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry* / Q000502:physiology; D004247:DNA / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000502:physiology; D008954:Models, Biological; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry*; D052898:Optical Tweezers; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000502:physiology; D013314:Stress, Mechanical; D020080:Tandem Repeat Sequences; D014157:Transcription Factors / Q000737:chemistry* / Q000502:physiology
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009707:Nucleosomes; C103337:RSC complex, S cerevisiae; C445179:SWI-SNF-B chromatin-remodeling complex; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D004247:DNA