Remodeling chromatin structures for transcription: what happens to the histones?
Activation of gene transcription in vivo is accompanied by an alteration of chromatin structure. The specific binding of transcriptional activators disrupts nucleosomal arrays, suggesting that the primary steps leading to transcriptional initiation involve interactions between activators and chromatin. The affinity of transcription factors for nucleosomal DNA is determined by the location of recognition sequences within nucleosomes, and by the cooperative interactions of multiple proteins targeting binding sites contained within the same nucleosomes. In addition, two distinct types of enzymatic complexes facilitate binding of transcription factors to nucleosomal DNA. These include type A histone acetyltransferases (e.g. GCN5/ADA transcriptional adaptor complex) and ATP-driven molecular machines that disrupt histone-DNA interactions (e.g. SWI/SNF and NURF complexes). These observations raise the important question of what happens to the histones during chromatin remodeling. We discuss evidence supporting the retention of histones at transcription factor-bound sequences as well as two alternative pathways of histone loss from gene control elements upon transcription factor binding: histone octamer sliding and histone dissociation.
Steger
D J
DJ
Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park 16802-4500, USA.
Workman
J L
JL
D000123:Acetyltransferases / Q000502:physiology; D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate / Q000502:physiology; D002843:Chromatin / Q000502:physiology / Q000648:ultrastructure*; D002868:Chromosomal Proteins, Non-Histone; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D005057:Eukaryotic Cells / Q000378:metabolism / Q000648:ultrastructure; D005656:Fungal Proteins / Q000502:physiology; D051548:Histone Acetyltransferases; D006657:Histones / Q000502:physiology*; D046911:Macromolecular Substances; D008954:Models, Biological; D009687:Nuclear Proteins; D009707:Nucleosomes / Q000378:metabolism* / Q000648:ultrastructure; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic
D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006657:Histones; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D009707:Nucleosomes; C084011:SMARCA2 protein, human; C078562:SWI1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000255:Adenosine Triphosphate; D004247:DNA; D000123:Acetyltransferases; D051548:Histone Acetyltransferases; D000251:Adenosine Triphosphatases; C499333:SNF2 protein, S cerevisiae