Precursor mRNA

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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", "mature mRNA", or simply "mRNA".

Processing

Eukaryotic pre-mRNA exists only briefly before it is fully processed into mRNA. Pre-mRNAs include two different types of segments, exons and introns. 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

v t e Post-transcriptional modification

Nuclear	Precursor mRNA 5′ cap formation Polyadenylation CPSF CstF PAP PAB2 CFI CFII Poly(A)-binding protein RNA splicing: intron/exon snRNP spliceosome minor spliceosome U1 alternative splicing pre-mRNA processing factor PLRG1 PRPF3 PRPF4 PRPF4B PRPF6 PRPF8 PRPF18 PRPF19 PRPF31 PRPF38A PRPF38B PRPF39 PRPF40A PRPF40B RNA editing Polyuridylation

Cytosolic	5′ cap methylation Messenger RNA decapping: DCP1A DCP1B DCP2 DCPS EDC3 EDC4

see also: disorders of transcription and post transcriptional modification, Transcription B bsyn: dna (repl, cycl, reco, repr) · tscr (fact, tcrg, nucl, rnat, rept, ptts) · tltn (risu, pttl, nexn) · dnab, rnab/runp · stru (domn, 1°, 2°, 3°, 4°)

Types of nucleic acids

Constituents

Nucleobases
Nucleosides
Nucleotides
Deoxynucleotides

Ribonucleic acids
(coding and non-coding)

translation:	mRNA pre-mRNA/hnRNA tRNA rRNA tmRNA

regulatory:	miRNA siRNA piRNA aRNA RNAi RNA processing: snRNA snoRNA Y RNA

other/ungrouped:	gRNA shRNA stRNA ta-siRNA SgRNA Sutherland RNA

Deoxyribonucleic acids

Nucleic acid analogues

XNA ( GNA / TNA / HNA )
LNA
PNA
morpholino

Cloning vectors

Biochemical families: carbohydrates
- alcohols
- glycoproteins
- glycosides
lipids
- eicosanoids
- fatty acids / intermediates
- phospholipids
- sphingolipids
- steroids
nucleic acids
- constituents / intermediates
proteins
- Amino acids / intermediates
tetrapyrroles / intermediates

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