Eukaryotes chromatin remodeling

Chromatin Remodeling Is an Important Aspect of Eukaryotic Gene Expression... 

However, the packing of DNA into nucleosome-like structures is not unique to eukarya similar structures appear in archaea (reviewed in Reeve et al., 1997). Additionally, histones and minichromosome maintenance proteins (MCM) are widespread among eukarya and archaea and absent in prokarya, and the eukaryotic chromo domain has a structure that is highly reminiscent of archaeal histones that are involved in formation of archaeal chromatin (Ball et al., 1997). Consequently, it is possible that chromatin remodeling in eukaryotes is an elaboration of a similar cellular mechanism in archaea. 

Thoma NH, Czyzewski BK, Alexeev AA, Mazin AV, Kowalczykowski SC, Pavletich NP (2005) Structure of the SW12/SNF2 chromatin-remodeling domain of eukaryotic Rad54. Nat Struct Mol Biol 12 350-356... 

Davie, J.R. and Moniwa, M. (2000) Control of chromatin remodeling. Crit. Rev. Eukaryot. Gene Expr. 10, 303-325. 

D. Expression of eukaryotic genes also depends on changes in chromatin structure, called chromatin remodeling. 

See also RNA Polymerase I Transcription, RNA Polymerase III Transcription, RNA Polymerase II Transcription, Chromatin Structure and Transcription, Eukaryotic Transcription. Termination of Eukaryotic Transcription, Chromatin Remodeling, Transcription Factor Binding Domains... 

See also RNA Polymerase II Transcription, Termination of Eukaryotic Transcription, Chromatin Remodeling... 

Eukaryotes Regulation of gene expression at the level ofDNA. In eukaryotes, activation of a gene requires changes in the state of chromatin (chromatin remodeling) that are facilitated by acetylation of histones and methylation of bases. These changes in DNA determine which genes are available for transcription. 

In eukaryotic organisms, DNA exists in a chromatin-bound state, with accessibility related to transcriptional status. It seems likely that the chromatin state will influence the ability of BER enzymes to search for and repair damage. Indeed a recent study has shown that nucleosome-bound DNA can be acted on by UDG and AP endonuclease, but not by DNA polymerase j3 (Beard et al, 2003). These results indicate that chromatin remodeling is necessary for completion of the BER process, but not for the recognition of damage. However, in another study, polymerase j3 was active upon nucleosome-bound substrates (Nilsen et al, 2002), though it is possible that the nucleosomal structures were more loosely packed in this study. Further efforts are necessary to establish the unique requirements of BER on a chromatin substrate. 

MURO-PASTEUR, M.I., GONZALEZ, R., STRAUSS, J., NARENDJA, F., SCAZZOCCHIO, C., The GATA factor AreA is essential for chromatin remodelling in a eukaryotic bidirectional promoter, EMBOJ., 1999,18, 1584-1597. 

Finally, the binding of specific transcription factors to cognate DNA elements may result in disruption of nucleosomal structure. Many eukaryotic genes have multiple protein-binding DNA elements. The serial binding of transcription factors to these elements—in a combinatorial fashion—may either directly disrupt the structure of the nucleosome or prevent its re-formation or recruit, via protein-protein interactions, multiprotein coactivator complexes that have the ability to covalently modify or remodel nucleosomes. These reactions result in chromatin-level structural changes that in the end increase DNA accessibifity to other factors and the transcription machinery. 

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