機(jī)體的細(xì)胞并非是一成不變的,，它們可以隨時(shí)轉(zhuǎn)變其形狀,，但這種變化往往是一種危險(xiǎn)信號,，如良性細(xì)胞就可能轉(zhuǎn)變成癌變細(xì)胞。如果能夠找到導(dǎo)致細(xì)胞發(fā)生這一轉(zhuǎn)變的機(jī)制,，將使科學(xué)家更好地了解許多不同的細(xì)胞——如干細(xì)胞轉(zhuǎn)變成癌細(xì)胞的過程,。了解這種轉(zhuǎn)變機(jī)制也有助于科學(xué)家找到治療一些疾病的方法。
Jeffrey Laney通過對釀酒酵母(Saccharomyces cerevisae)研究發(fā)現(xiàn),，釀酒酵母在完成自我受精(self-fertilize)的過程中,，其細(xì)胞形狀由“a”字形轉(zhuǎn)變成為“α(alpha)”形狀。
在釀酒酵母細(xì)胞內(nèi),，存在一種調(diào)節(jié)蛋白,，該調(diào)節(jié)蛋白能結(jié)合到細(xì)胞內(nèi)某個(gè)基因上形成一個(gè)“帽”結(jié)構(gòu)，調(diào)控基因的表達(dá),，從而實(shí)現(xiàn)細(xì)胞在不同形狀之間的轉(zhuǎn)變,。
雖然該課題組研究的這類基因在人類基因組中并不存在，但是研究人員認(rèn)為,，這種通過調(diào)控基因的開啟和關(guān)閉來實(shí)現(xiàn)細(xì)胞不同形狀的改變，應(yīng)該在所有細(xì)胞中普遍存在,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature Cell Biology 11, 1481 - 1486 (2009) 15 November 2009 | doi:10.1038/ncb1997
A ubiquitin-selective AAA-ATPase mediates transcriptional switching by remodelling a repressor–promoter DNA complex
Alexander J. Wilcox1 & Jeffrey D. Laney1
Switches between different phenotypes and their underlying states of gene transcription occur as cells respond to intrinsic developmental cues or adapt to changing environmental conditions. Post-translational modification of the master regulatory transcription factors that define the initial phenotype is a common strategy to direct such transitions. Emerging evidence indicates that the modification of key transcription factors by the small polypeptide ubiquitin has a central role in many of these transitions1, 2. However, the molecular mechanisms by which ubiquitylation regulates the switching of promoters between active and inactive states are largely unknown. Ubiquitylation of the yeast transcriptional repressor 2 is necessary to evoke the transition between mating-types3, and here we dissect the impact of this modification on 2 dynamics at its target promoters. Ubiquitylation of 2 does not alter DNA occupancy by depleting the existing pool of the transcription factor, despite its well-characterized function in directing repressor turnover. Rather, 2 ubiquitylation has a direct role in the rapid removal of the repressor from its DNA targets. This disassembly of 2 from DNA depends on the ubiquitin-selective AAA-ATPase Cdc48. Our findings expand the functional targets of Cdc48 to include active transcriptional regulatory complexes in the nucleus. These data reveal an ubiquitin-dependent extraction pathway for dismantling transcription factor–DNA complexes and provide an archetype for the regulation of transcriptional switching events by ubiquitylation.
Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Box G-L2, Providence, RI 02912, USA.
