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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/02/06 22:16:37」(JST)

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mRNA前駆体（エムアールエヌエーぜんくたい）は、スプライシングなどのさまざまな加工を受けて成熟した mRNA になる前の RNA 分子。

一般に真核生物では、タンパク質をコードする遺伝子の多くがイントロンを持つ。これらの遺伝子は細胞核内でRNAに転写され一次転写産物となる。これはヘテロ核 RNA (hnRNA) とも呼ばれる。その後5' 末端へメチル化されたグアノシンが付加する5'キャップ、RNAスプライシングによるイントロンの除去、3' 末端に多数が数珠状に連なったアデニル酸が付加するポリA尾部といった装飾を経て、成熟mRNAとなる。このようにして出来た mRNA は核外に輸送され翻訳される。

一方で酵母や植物のミトコンドリア、葉緑体のゲノムにも、タンパク質をコードする遺伝子に自己スプライシングイントロンを持つ物があり、これらの一次転写産物も mRNA 前駆体の一種である。

DNA
EEEEEEEEEEEiiiiiiiiiiiiEEEEEEEEEEEEE
EEEEEEEEEEEiiiiiiiiiiiiEEEEEEEEEEEEE


          転写  ↓

mRNA前駆体
EEEEEEEEEEEiiiiiiiiiiiiEEEEEEEEEEEEE

    プロセシング ↓

mRNA
 CEEEEEEEEEEEEEEEEEEEEEEEAAAAAAAAA

核外への輸送・翻訳  ↓

タンパク質
           XXXXXXXXXX

E:エクソン i:イントロン C:キャップ構造 AAAAA: ポリA尾部 X:アミノ酸

この項目は、生物学に関連した書きかけの項目です。この項目を加筆・訂正などしてくださる協力者を求めています（プロジェクト:生命科学／Portal:生物学）。

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[Wiki en表示]

Pre-mRNA is the first form of RNA created through transcription in protein synthesis. The pre-mRNA lacks structures that the messenger RNA (mRNA) requires. First all introns have to be removed from the transcribed RNA through a process known as splicing. Before the RNA is ready for export, a Poly(A)tail is added to the 3’ end of the RNA and a 5’ cap is added to the 5’ end.

See main article Primary transcript for more details

Precursor mRNA (pre-mRNA) is an immature single strand of messenger ribonucleic acid (mRNA). Pre-mRNA is synthesized from a DNA template in the cell nucleus by transcription. Pre-mRNA comprises the bulk of heterogeneous nuclear RNA (hnRNA). The term hnRNA is often used as a synonym for pre-mRNA, although, in the strict sense, hnRNA may include nuclear RNA transcripts that do not end up as cytoplasmic mRNA.

Once pre-mRNA has been completely processed, it is termed "mature messenger RNA", or simply "messenger RNA".

Processing

Eukaryotic pre-mRNA exists only briefly before it is fully processed into mRNA. Pre-mRNAs are built from 5'UTRs (directly upstream from the initiation codon), different number of exons and introns and 3'UTRs which immediately follows the translation termination codon. Exons are segments that are retained in the final mRNA, whereas introns are removed in a process called splicing, which is performed by the spliceosome (except for self-splicing introns).

Additional processing steps attach modifications to the 5' and 3' ends of Eukaryotic pre-mRNA. These include a 5' cap of 7-methylguanosine and a poly-A tail. In addition, eukaryotic pre-mRNAs have their introns spliced out by spliceosomes made up of small nuclear ribonucleoproteins.^[1]^[2]

When a pre-mRNA strand has been properly processed to an mRNA sequence, it is exported out of the nucleus and eventually translated into a protein – a process accomplished in conjunction with ribosomes.

References

^ Weaver, Robert F. (2005). Molecular Biology, p.432-448. McGraw-Hill, New York, NY. ISBN 0-07-284611-9.
^ Wahl, M. C.; Will, C. L.; Lührmann, R. (2009). "The Spliceosome: Design Principles of a Dynamic RNP Machine". Cell. 136 (4): 701–718. doi:10.1016/j.cell.2009.02.009. PMID 19239890.

External links

Scienceden.com RNA Article

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English Journal

RNA-binding proteins with prion-like domains in health and disease.

Harrison AF1,2, Shorter J3,2.
The Biochemical journal.Biochem J.2017 Apr 7;474(8):1417-1438. doi: 10.1042/BCJ20160499.
PMID 28389532

Long non-coding RNA LINC00672 contributes to p53 protein-mediated gene suppression and promotes endometrial cancer chemosensitivity.

Li W1, Li H2, Zhang L3, Hu M4, Li F1, Deng J1, An M1, Wu S1, Ma R1, Lu J5, Zhou Y6.
The Journal of biological chemistry.J Biol Chem.2017 Apr 7;292(14):5801-5813. doi: 10.1074/jbc.M116.758508. Epub 2017 Feb 23.
PMID 28232485

Identification and dynamic changes of RNAs isolated from RALY-containing ribonucleoprotein complexes.

Rossi A1, Moro A1, Tebaldi T2, Cornella N1, Gasperini L1, Lunelli L3, Quattrone A2, Viero G4, Macchi P1.
Nucleic acids research.Nucleic Acids Res.2017 Apr 4. doi: 10.1093/nar/gkx235. [Epub ahead of print]
PMID 28379492

Japanese Journal

4.カイニン酸誘発てんかんによるラット視床下部CRHmRNAおよびVasopressin hnRNAの発現の変化

産業医科大学雑誌 22(1), 71, 2000-03-01
NAID 110001261521

Different Expression of Immediate-Early Genes in the Rat Paraventricular Nucleus Induced by Stress: Relation to Corticotropin-Releasing Factor Gene Transcription.:Relation to Corticotropin-Releasing Factor Gene Transcription