RNA modifications: 5 prime cap

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In molecular biology, the 5′ cap is a specially altered nucleotide on the 5′ end of precursor messenger RNA and some other primary RNA transcripts as found in eukaryotes. The process of 5′ capping is vital to creating mature messenger RNA, which is then able to undergo translation. Capping ensures the messenger RNA's stability while it undergoes translation in the process of protein synthesis, and is a highly regulated process that occurs in the cell nucleus. Because this only occurs in the nucleus, mitochondrial and chloroplast mRNA are not capped.
The 5′ cap is found on the 5′ end of an mRNA molecule and consists of a guanine nucleotide connected to the mRNA via an unusual 5′ to 5′ triphosphate linkage. This guanosine is methylated on the 7 position directly after capping in vivo by a methyl transferase. It is referred to as a 7-methylguanylate cap, abbreviated m7G. Further modifications include the possible methylation of the 2′ hydroxy-groups of the first 2 ribose sugars of the 5′ end of the mRNA. The methylation of both 2′ hydroxy-groups is shown on the diagram. The 5′ cap looks like the 3′ end of an RNA molecule (the 5′ carbon of the cap ribose is bonded, and the 3′ unbonded). This provides significant resistance to 5′ exonucleases.
The 5′ cap has 4 main functions:
Regulation of nuclear export.
Prevention of degradation by exonucleases.
Promotion of translation (see ribosome and translation).
Promotion of 5′ proximal intron excision.[1]
Nuclear export of RNA is regulated by the Cap binding complex (CBC), which binds exclusively to capped RNA. The CBC is then recognized by the nuclear pore complex and exported. Once in the cytoplasm after the pioneer round of translation, the CBC is replaced by the translation factors eIF-4E and eIF-4G. This complex is then recognized by other translation initiation machinery including the ribosome.[2]
Cap prevents 5′ degradation in two ways. First, degradation of the mRNA by 5′ exonucleases is prevented (as mentioned above) by functionally looking like a 3′ end. Second, the CBC complex and the eIF-4E/eIF-4G block the access of decapping enzymes to the cap. This increases the half-life of the mRNA, essential in eukaryotes as the export process takes significant time.
Decapping of an mRNA is catalyzed by the decapping complex made up of at least Dcp1 and Dcp2, which must compete with eIF-4E to bind the cap. Thus the 5′ cap is a marker of an actively translating mRNA and is used by cells to regulate mRNA half-lives in response to new stimuli. Undesirable mRNAs are sent to P-bodies for temporary storage or decapping, the details of which are still being resolved.[3]
The mechanism of 5′ proximal intron excision promotion is not well understood, but the 5′ cap appears to loop around and interact with the spliceosome in the splicing process, promoting intron excision. Source of the article published in description is Wikipedia. I am sharing their material. Copyright by original content developers of Wikipedia.
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[@sheeezashoukat6068]

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[@prabirsbiology8220]

Why guanine is used in capping in m RNA besides other. Plz reply. It is very helpful to me.

[@dikshaapadhi1285]

Hello! Could you kindly make a video on the Role of RNA modifications in cancer. It will be really helpful.

[@duebelknuebel]

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greets from Germany

[@moahhed121]

Powerful explanation!

[@chaschassasafras8700]

You don't explain how the first base in 5' in mRNA loses one phosphate group. The 5'-5' linkage contains one phosphate from the GTP and 2 from the base in mRNA. However, this base originally contains 3 phosphate groups. How does it lose the third phosphate group?

[@ahmadal_shanqeety802]

By an enzyme "RNA triphosphatase" which cleaves the third P of the growing RNA leaving only diphosphate

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[@kishan1851]

Apart from the hilarious accent and your mom's intrusion, this was actually very informative. Thanks a lot!

[@rkcraft2550]

Why there is used only GTP not any other for capping?

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[@nooriyajameel8035]

Can you please tell me that why capping is only done with guanine?? Why not with other nucleotides??
I have searched enough but didn't get any answer to this

[@markjuanico9540]

you really helped me a lot man! thanks

[@sikhapanigrahi826]

Sir, you told two phosphates are released. But in the book,it is given that one phosphate is removed by the enzyme phosphohydrolase.

[@rizwanullah6467]

What is the name of that book plz tell

[@dianagh8812]

best video ever

[@shomusbiologyofficial]

Thank you

[@swarnabhasarkar8702]

Sir... I've a question... The α phosphate of the incoming dGTP and the α and β phosphate of the 5' RNA end is getting attached... Right?

[@muhammadwaqar648]

sir by adding 5cap to messenger RNA we can only protect from exonuclease but how can we protect RNA from endonuclease at the middle cleavag

[@samerghanem599]

very precise, great explanation

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[@patitpaban5542]

Why G is only used in capping?

[@juliawocyrus7577]

Great explanation....thanks

[@Divyajyoti__]

Thank you sir🙏

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[@kochutheresaa]

why G is used in capping?

[@binduu19]

hello sir.I have a doubt in synthesis of eukaryotic mRNAs by RNA poly 2
I don't understand.. I just understand d process of termination...will u pls explain the process before termination...that is initiation and elongation....

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+Jyoti Chandan you're welcome

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[@chatpatabullet...3172]

Nice explanation😊

[@sikhapanigrahi826]

Sir sometimes two guanosine residues are added instead of one.. Please explain it.

[@omniamohamed404]

What is the difference between Guanine and Guanosine?

[@omniamohamed404]

Why do the original nucleotide of 5 prime end have 2 phosphate groups? 13:02

[@priyak6945]

Thanks sir

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[@Vishal5171]

Sir capping process is cotranscriptional...

[@tasbeehashraf1810]

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[@hamsinikaruturi4653]

Then where does that third phosphate go or how it is released from first base of m.rna ?

[@alfredomunoz8791]

Is this addition of a 5’ cap modificationfor eukaryotes prokaryotes or both?

[@shomusbiologyofficial]

Eukaryotes only

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[@mampidutta327]

it helped a lot. .. suman

[@geparada88]

Nice! But mRNA capping is not post-transcriptional, but rather co-transcriptional.

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+Parveen Akther you're welcome

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Plz vedio on biochemistry of methanogens with there reaction tnd steps

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Please add caption subtitle

[@hasankuliyev4211]

is in Base 1 initially three phosphates instead of two that u said

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[@raginirajput2348]

what is exonucleus?

[@biologicalresearch5836]

Ability of polymerise enzyme to remove the wrongly incorportaed nucleotide .

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