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【bio-news】基因组的开与关
02/22/07 -- At any given time, most of the roughly 30,000 genes that constitute the human genome are inactive, or repressed, closed to the cellular machinery that transcribes genes into the proteins of the body. In an average cell, only about one in ten genes is active, or expressed, at any given moment, with its DNA open to the cell' transcriptional machinery.
A dynamic cast of gatekeeper enzymes controls this access to the DNA, adding and removing particular molecules to open or close the genome to transcription as needed. Fully explicating the complex interplay among these enzymes and the molecules they manage has been a primary goal for scientists seeking to understand the mechanisms governing gene control. These mechanisms are vital for health-- when they go wrong, diseases like cancer can result.
In study published online February 22 in Cell, researchers at The Wistar Institute identify an important new player in this gene-control system, an enzyme responsible for removing certain molecules, or marks, involved in opening or closing chromatin, the material that makes up chromosomes. The activity of this enzyme is thought to be widespread in the genome, likely affecting many genes.
"This enzyme removes methyl groups from a specific location where they facilitate opening of the chromatin for gene expression, and therefore this enzyme maintains a repressed state of gene expression," says Ramin Shiekhattar, Ph.D., a professor at The Wistar Institute and senior author on the Cell study. Currently, Shiekhattar is also a professor at the Center de Regulacio Genomica in Barcelona. "When the enzyme is not present, however, the marks are not removed, and the chromatin remains open for transcription."
The enzyme, called JARID1d, is the first identified member of a new family of enzymes that removes trimethylation from histone H3 at the lysine 4 location. Histones are critical components of chromatin. In mammalian genomes, trimethyl groups at the lysine 4 location of this histone have been known to be associated with gene activation. Shiekhattar and his team hypothesized the existence of an enzyme that would remove these trimethyl groups.
"We and others had wondered whether there might not be an enzyme able to remove these trimethyl marks," says Shiekhattar. "Such an enzyme would have the effect of setting the genes back to their original repressed state."
An important aspect of the work by Shiekhattar and his colleagues is their demonstration of an intimate connection between the histone demethylase enzyme JARID1d and Ring6a, a polycomb-like protein. Polycomb proteins are also known to play an important role in gene repression. Indeed, the findings show that Ring6a has the ability to regulate the enzymatic activity of the histone demethylase in vitro as well as in vivo. These results extend the role of transcriptional inhibitory polycomb complexes through their physical and functional link with histone demethylase enzymes.
Source: The Wistar Institute
http://www.bio.com/newsfeatures/newsfeatures_research.jhtml?cid=26400014 本人已认领该文编译，48小时后若未提交译文，请其他战友自由认领。 基因组的开与关Opening and Closing the Genome
02/22/07 -- At any given time, most of the roughly 30,000 genes that constitute the human genome are inactive, or repressed, closed to the cellular machinery that transcribes genes into the proteins of the body. In an average cell, only about one in ten genes is active, or expressed, at any given moment, with its DNA open to the cell' transcriptional machinery.
02/22/07，任何时候组成人类基因组的大约3000个基因是不活动的或者说是被抑制的，细胞内这3000个基因转录成蛋白的通路通常是关闭的。对一个细胞而言，10个基因中仅有1个是活动的，或者说是表达的，在任何时刻, 这个基因都开放给细胞的转录机器。
A dynamic cast of gatekeeper enzymes controls this access to the DNA, adding and removing particular molecules to open or close the genome to transcription as needed. Fully explicating the complex interplay among these enzymes and the molecules they manage has been a primary goal for scientists seeking to understand the mechanisms governing gene control. These mechanisms are vital for health-- when they go wrong, diseases like cancer can result.
一个动态的酶通过增加和去除特定的分子从而实现基因组的转录开关的开和关。充分阐明这些酶和它们管理的蛋白分子间复杂的相互作用已成为科学家们了解基因调控机制的首要目标。 这些机制对健康至关重要—一旦出现问题, 就可能导致机体患上如癌症之类的疾病。
In study published online February 22 in Cell, researchers at The Wistar Institute identify an important new player in this gene-control system, an enzyme responsible for removing certain molecules, or marks, involved in opening or closing chromatin, the material that makes up chromosomes. The activity of this enzyme is thought to be widespread in the genome, likely affecting many genes.
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作者:admin@医学,生命科学 2011-02-25 17:14
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