SWI/SNF stimulates the formation of disparate activator-nucleosome complexes but is partially redundant with cooperative binding.
To investigate the potential mechanisms by which the SWI/SNF complex differentially regulates different genes we have tested whether transcription factors with diverse DNA binding domains were able to exploit nucleosome disruption by SWI/SNF. In addition to GAL4-VP16, the SWI/SNF complex stimulated nucleosome binding by the Zn2+ fingers of Sp1, the basic helix-loop-helix domain of USF, and the rel domain of NF-kappaB. In each case SWI/SNF action resulted in the formation of a stable factor-nucleosome complex that persisted after detachment of SWI/SNF from the nucleosome. Thus, stimulation of factor binding by SWI/SNF appears to be universal. The degree of SWI/SNF stimulation of nucleosome binding by a factor appears to be inversely related to the extent that binding is inhibited by the histone octamer. Cooperative binding of 5 GAL4-VP16 dimers to a 5-site nucleosome enhanced GAL4 binding relative to a single-site nucleosome, but this also reduced the degree of stimulation by SWI/SNF. The SWI/SNF complex increased the affinity of 5 GAL4-VP16 dimers for nucleosomes equal to that of DNA but no further. Similarly, multimerized NF-kappaB sites enhanced nucleosome binding by NF-kappaB and reduced the stimulatory effect of SWI/SNF. Thus, cooperative binding of factors to nucleosomes is partially redundant with the function of the SWI/SNF complex.
Utley
R T
RT
Department of Biochemistry and Molecular Biology and The Center for Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania 16802-4500, USA.
Côté
J
J
Owen-Hughes
T
T
Workman
J L
JL
D000255:Adenosine Triphosphate / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D004247:DNA / Q000378:metabolism; D018983:DNA Footprinting; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000378:metabolism*; D046911:Macromolecular Substances; D008958:Models, Molecular; D016328:NF-kappa B / Q000378:metabolism; D009687:Nuclear Proteins; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000378:metabolism*; D000071796:SMARCB1 Protein; D029701:Saccharomyces cerevisiae Proteins; D016329:Sp1 Transcription Factor / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors
D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C070633:Gal-VP16; D046911:Macromolecular Substances; D016328:NF-kappa B; D009687:Nuclear Proteins; D009707:Nucleosomes; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; C094753:SNF11 protein, S cerevisiae; C101683:SNF12 protein, S cerevisiae; C072981:SWI3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D016329:Sp1 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D004247:DNA