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专业背景:计算机科学 研究方向与兴趣: JavaEE-Web软件开发, 生物信息学, 数据挖掘与机器学习, 智能信息系统 目前工作: 基因组, 转录组, NGS高通量数据分析, 生物数据挖掘, 植物系统发育和比较进化基因组学

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WHAT IS "UTR"  

2011-08-17 11:16:59|  分类: 遗传与基因组学 |  标签: |举报 |字号 订阅

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 WHAT IS UTR - moonlight - moonlight博客

WHAT IS UTR - moonlight - moonlight博客

mature eukaryotic mRNA的结构。一个完整的 mRNA 包括有 5'端帽5'非转译区编码区3'非转译区和poly(A)尾链。

1. UTR   UTR(Untranslated Regions)即非翻译区,是mRNA分子两端的非编码片段。

  5'-UTR从mRNA起点的甲基化鸟嘌呤核苷酸帽延伸至AUG起始密码子,3'-UTR从编码区末端的终止密码子延伸至多聚A尾巴(Poly-A)的末端。

2. UTR    (From Wikipedia, the free encyclopedia)

UTR, which stands for Untranslated Region, refers to either of two sections on each side of a coding sequence on a strand of mRNA. If it is found on the 5' side, it is called the 5' UTR (also known as the Leader Sequence), or if it is found on the 3' side, it is called the 3' UTR.

3.   3' UTR.-----Three prime untranslated region

The three prime untranslated region (3' UTR) is a particular section of messenger RNA (mRNA). It follows the coding region.

An mRNA molecule codes for a protein through translation. The mRNA also contains regions that are not translated. In eukaryotes真核生物 these regions are the cap, 5' untranslated region, 3' untranslated region, and polyA tail (see diagram).

In prokaryotes原核生物 mRNA structures have some differences (see mRNA) as do histone mRNAs. However, both have 3' UTRs.

Several regulatory sequences are found in the 3' UTR:

  • A polyadenylation signal, usually AAUAAA, or a slight variant. This marks the site of cleavage of the transcript approximately 30 base pairs past the signal, followed by the addition of several hundred adenine residues (poly-A tail).
  • Binding sites for proteins, that may affect the mRNA's stability or location in the cell, like SECIS elements (which direct the ribosome to translate the codon UGA as selenocysteines rather than as a stop codon), or AU-rich elements (AREs), stretches consisting of mainly adenine and uracil nucleotides (which can either stabilize or destabilize the mRNA depending on the protein bound to it).
  • Binding sites for miRNAs, a type of RNAi.

4. Five prime untranslated region

The five prime untranslated region (5' UTR), also known as the leader sequence, is a particular section of messenger RNA (mRNA) and the DNA that codes for it. It starts at the +1 position (where transcription begins) and ends just before the start codon (usually AUG) of the coding region. It usually contains a ribosome binding site (RBS), in bacteria also known as the Shine Dalgarno sequence (AGGAGGU). The 5' UTR may be a hundred or more nucleotides long, and the 3' UTR may be even longer (up to several kilobases in length) [1].

An mRNA molecule codes for a protein through translation. The mRNA also contains regions that are not translated: in eukaryotes this includes the 5' untranslated region, 3' untranslated region, 5' cap and poly-A tail.

In prokaryotic mRNA the 5' UTR is normally short. Some viruses and cellular genes have unusual long structured 5' UTRs which may have roles in gene expression.

 Several regulatory sequences may be found in the 5' UTR:

  • Binding sites for proteins, that may affect the mRNA's stability or translation, for example iron responsive elements, which occur in the 5' UTRs (and 3' UTRs) of a small number of eukaryotic mRNAs that regulate gene expression in response to iron.
  • Regulatory elements that do not depend on proteins, such as riboswitches.
  • Sequences that promote the initiation of translation.

5. 请教:启动子、外显子、内含子和UTR关系的问题

本帖引用网址:http://bbs.bbioo.com/thread-27693-1-1.html

如题:

(1)基因有内含子外显子之分,那么在mRNA上的UTR区在DNA序列中是算内含子还是外显子?为什么?

(2)一个完整的基因应该包括启动子,那么启动子序列应该即不属于内含子也不属于外显子吧?

(3)每个基因之间都有一定的间隔序列,这些基因间的间隔序列应该不属于内含子吧,因为内含子是处在外显子之间的。那么这些基因间的间隔序列又称为什么?其功能又是什么?

解释 :

a  。启动子的定义是能过被聚合酶识别、结合并能启动转录的DNA序列,所以说核心启动子应该包括了TAbox,是RNA聚合酶的识别位点,当然还有caat区,gc区等如果把增强子算在里面我觉得也没有什么错误,毕竟他为转录的强度作出了巨大的贡献。启动子在mrna上应该只有起始点的一部分序列得到显示。非转录区应该包括两个部位,一个是与核糖体识别结合即充当滑动轨道的序列,在原核中成为SD序列,在真核中的名字很拗口,一直没记住。当核糖体与5端的SD序列结合后滑动找到启示密码子。另一个是真核3端的加尾信号后的一段序列,其实这个序列很长并且有两处保守的位点,当加尾时被加尾酶识别,并有其他的辅助因子切除5端保守序列以后的部分然后加尾。

两个不同基因是通过一种叫做居间序列隔开的,他能基因的增强子或者转录保持在一定的范围,具体的内容好像现在还不清楚。基因之间的隔离有异染色质的特点,而隔离子就是防止异染色质的间隔与活性染色质的交叉影响。

[ 本帖最后由 zhengao2006 于 2008-9-29 20:45 编辑 ]

b。 多读定义好处多!!!呵呵

内含子(introns)定义:在转录后的加工中,从最初的转录产物除去的内部的核苷酸序列。

外显子(exons)定义:既存在于最初的转录产物中,也存在于成熟的RNA分子中的核苷酸序列。

非翻译区(untranslated region)定义:mRNA分子两端的非编码片段;5'-UTR从mRNA起点的甲基化鸟嘌呤核苷酸帽延伸至AUG起始密码子,又称前导区(leader),而3'-UTR从编码区末端的终止密码子延伸至多聚A尾巴(Poly-A)的末端,又称尾区(trailer)。

所以对于对于第一个疑问,我想首先我们应该清楚了。不管是内含子、外显子还是UTR都是mRNA的一部分,而他们所在的位置是截然不同的,对于真核生物基因从5’向3‘方向角度说按顺序那便是前导区的5'-UTR、编码区的外显子和内含子、3’-UTR。这是第一问。

6. 真核生物mRNA 3’非翻译区的调控功能

摘要:真核生物mRNA 3’非翻译区可以调节转录本的稳定性、亚细胞定位和翻译水平,决定某一特定mRNA的命运,是许多基因表达所必需的一个调节区。3’ 非翻译区介导的功能的修饰可影响一个或多个基因的表达,从而导致疾病的发生。对相关mRNA 3’ 非翻译区的调节序列和与这些序列特异结合的蛋白质等具体信息的认识,将成为药物设计的新的分子靶。

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