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【转贴】中心粒里的RNA基因组？
由 immuno05 Wednesday, June 07 @ 17:37:40 CST
http://www.dnathink.org/modules.php?name=News&file=article&sid=267
转自医网琴声
翻译一下：
基因组是 有编码蛋白质的DNA组成，但是细胞核的一个关键部分还有一种特
有的基因组，它由RNA构成，而RNA通常是从基因
到蛋白质的中介物——这意味着这种奇怪的实体可
能是RNA世界的一个分子遗迹，它先于DNA的进化并
使人们更加相信生命最初依赖于RNA的假说。
RNA存在于中心体（centrosome）。对细胞分裂至关
重要的中心体会在细胞分裂成两半之前向细胞的两
极运动。它们锚定在附着在被复制染色体上的蛋白
质链上，并帮助将姐妹染色体拉开，从而使每个新
细胞只有每条染色体的一个拷贝。在参与这项工作时，一个中心体本身会进行自我复制。数十
年来，研究人员一直争论这些锚是否有它们自己的“基因组”，如果是这样，那么它的核酸序列
是DNA还是RNA?
路易斯安那州立大学的Alliegro和他的妻子Mary Anne以及Rensselear Polytechnic研究院的
Robert Palazzo一直努力***这个疑团。
Palazzo花费大量精力从容易操作的浪蛤（surf clam）卵中获得中心体并对其进行核酸分析。
Alliegros分析了这种RNA，并发现5种与任何已知的RNA都不同的序列，并且在卵的其他部位
中没有发现这种RNA。研究人员发现其中一个片段编码一种复制RNA有关的酶——反转录酶
（reverse transcriptase）。这种酶可能促使中心体在形成第二个中心体时复制自己的RNA。
研究人员将这些发现公布在最新一期的《美国科学院院刊》上。
细胞中其他的细胞器如线粒体和叶绿体也有自己的DNA基因组，而中心体则似乎只有RNA。
但是，即使这个基因组中有一种反转录酶基因，RNA可能也不能复制而只是协助组织中心
体。
中心体只有RNA的发现可能重燃有关中心体基因组的“战火”。因此，该研究组还需要排出这
些RNA的存在是由病毒引入的可能性。但是，这项研究对解开这种细胞器的一些疑团仍然具有
重要意义。
ScienceNow-May 30,2006-A Genome for Cellular Anchors?
Genomes are made up of DNA that contains the recipes for proteins, but one crucial part of a cell's nucleus may have a unique kind of genome of its own, one spelled out in RNA, which is best known as a go-between in the production of proteins from genes. That means the oddball entity could be a molecular relic from the RNA world, which predated the evolution of DNA, lending credence to the idea that life depended first on RNA.
RNA is present in the centrosome, a glob of proteins essential to cell division, report cell biologist Mark Alliegro of Louisiana State University Health Sciences Center in New Orleans and colleagues. Centrosomes are key to cell division and move to opposite edges of a cell before it splits. They anchor strands of protein that attach to replicated chromosomes and help pull the paired chromosomes apart, so that each new cell gets just one copy of each chromosome. In anticipation of this task, a centrosome itself replicates. Researchers have argued for decades whether these anchors have their own "genome," and if so, whether its nucleic acid sequence is DNA or RNA.
Alliegro, his wife Mary Anne, also at LSU, and cell biologist Robert Palazzo from Rensselear Polytechnic Institute in Troy, New York, have begun to resolve this debate. Palazzo painstakingly picked out centrosomes from large and easily manipulated surf clam eggs and detected nucleic acids in the concentrated extract. The Alliegros analyzed this RNA, finding five sequences that looked nothing like any known RNA and that they couldn抰 find any place else in the egg. One piece codes for an enzyme involved in replicating RNA called reverse transcriptase, the researchers report online this week in the Proceedings of the National Academy of Sciences. If produced, this enzyme might enable the centrosome to copy its RNA as it forms a second centrosome.
Other organelles within a cell, such as mitochondria and chloroplasts, have their own genomes spelled out in DNA. The centrosome seems to have just RNA, Palazzo points out. However, even with a reverse transcriptase gene in the genome, the RNA may not replicate, but instead could simply help organize the centrosome or hold it together, he cautions.
The mere existence of this RNA, let alone its function, will likely reignite controversy about centrosomes, says Joel Rosenbaum, a cell biologist at Yale University. And the group will have to rule out viruses as the source of the RNA. But the work is still important in resolving some of the mystery about this cell component, Rosenbaum notes. "They have gone a step further than others have in the past."
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作者:admin@医学,生命科学 2011-02-27 17:11
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