Opening the chromatin for transcription.
Eukaryotic genomes are packaged into a dynamic hierarchy chromatin structure. In such a particular context, the transition from a repressed compacted chromatin to a rather extended fiber is necessary for transcription. The chromatin opening includes three events, the initial factor getting access to nucleosome DNA, local chromatin opening mediated by activator/coactivator, and transcription associated with extensive chromatin opening. Chromatin dynamics, which is DNA sequence dependent, and also occurs in condensed fiber, provides the opportunity for activators binding to DNA. Coactivators recruited by the activator open the chromatin locally. However, it appears that genes adopt distinct chromatin opening mechanisms according to whether the gene is induced expression, developmental and tissue-specific expression, or constitutive expression. In contrast to transcription initiation-related local chromatin opening, large scale of chromatin opening is associated with a functional enhancer as well as high transcription rate. How the transcription initiated from an enhancer or enhancer like modules, i.e. intergenic transcription, conducts the extensive chromatin opening is discussed. A model for long-range interaction that non-coding transcripts from enhancers may promote efficient communication with promoters is proposed.
Li
Ya-Jun
YJ
National Laboratory of Medical Molecular Biology, R514, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, 5 Dong Dan San Tiao, Beijing 100005, China. yj_li2003@yahoo.com
Fu
Xiang-Hui
XH
Liu
De-Pei
DP
Liang
Chih-Chuan
CC
D000818:Animals; D002843:Chromatin / Q000378:metabolism; D042002:Chromatin Assembly and Disassembly / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D006801:Humans; D046911:Macromolecular Substances; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
D002843:Chromatin; D046911:Macromolecular Substances