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Aínda que a secuencia de ADN de case todas as células dun organismo é a mesma, os patróns de unión dos [[factor de transcrición|factores de transcrición]] e os patróns correspondentes de expresión xénica son diferentes. En grande medida, as diferenzas na unión de factores de transcrición están determinados pola accesibilidade á cromatina dos seus sitios de unión por medio de [[modificación de histonas]] e/ou [[factor pioneiro|factores pioneiros]]. En particular, é importante saber se un [[nucleosoma]] está cubrindo un sitio de unión xenómico ou non. Estudos recentes dilucidaron o papel do posicionamento de nucleosomas durante o desenvolvemento de células nais.<ref name = "Teif_et_al">{{cite journal |pmid=23085715 | doi=10.1038/nsmb.2419 |author=Teif VB, Vainshtein Y, Caudron-Herger M, Mallm JP, Marth C, Höfer T, Rippe K. |title= Genome-wide nucleosome positioning during embryonic stem cell development |journal=Nat Struct Mol Biol. |year= 2012 | volume=19 |issue=11 |pages=1185–92}}</ref>
 
====RolePapel ofda signalingsinalización in epigeneticno control epixenético====
 
A final question to ask concerns the role of [[cell signaling]] in influencing the epigenetic processes governing differentiation. Such a role should exist, as it would be reasonable to think that extrinsic signaling can lead to epigenetic remodeling, just as it can lead to changes in gene expression through the activation or repression of different transcription factors. Interestingly, little direct data is available concerning the specific signals that influence the [[epigenome]], and the majority of current knowledge consist of speculations on plausible candidate regulators of epigenetic remodeling.<ref name = "Mohammad">{{cite journal |pmid=20944593 |doi=10.1038/nbt1010-1033 |author=Mohammad HP, Baylin SB |title=Linking cell signaling and the epigenetic machinery |journal=Nat Biotechnol |year=2010 |volume=28 |issue=10 |pages=1033–8}}</ref> We will first discuss several major candidates thought to be involved in the induction and maintenance of both embryonic stem cells and their differentiated progeny, and then turn to one example of specific signaling pathways in which more direct evidence exists for its role in epigenetic change.
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