imported>Citation bot: Removed proxy/dead URL that duplicated identifier. | Use this bot. Report bugs. | Suggested by SemperIocundus | #UCB_webform 1690/2500

2023-01-04T06:29:11Z

Removed proxy/dead URL that duplicated identifier. | Use this bot. Report bugs. | Suggested by SemperIocundus | #UCB_webform 1690/2500

New page

[[File:Cap-binding complex 1H2T.png|thumb|Surface model of the cap-binding complex (heavy chain pink, light chain yellow, m7G and GDP as balls), after PDB 1H2T.]]
{{short description|Formation on 5' ends of mRNAs}}
The [[5' cap]] of eukaryotic [[messenger RNA]] is bound at all times by various '''cap-binding complexes''' ('''CBCs''').

==Nuclear cap-binding complex==

In the nucleus, freshly transcribed mRNA molecules are bound on the 5' cap by the [[nuclear cap-binding protein complex|nuclear cap-binding complex]] of Cbc1/Cbc2 in yeast or CBP20/CBP80 in metazoans. These aid in the export of the mRNA and protect it from [[Messenger RNA decapping|decapping]]. They also serve as a marker for the so-called pioneer round of translation when the message is examined by [[nonsense mediated decay]].<ref name=Isken2007>{{citation | last1 = Isken | first1 = O. | last2 = Maquat | first2 = L.E. | year = 2007 | title = Quality control of eukaryotic mRNA: safeguarding cells from abnormal mRNA function | journal = Genes & Development | volume = 21 | issue = 15 | pages = 1833–56 | pmid = 17671086 | doi = 10.1101/gad.1566807| doi-access = free }}</ref>

==Cytoplasmic cap-binding complex==

After the first round of translation ("pioneer round"), CBC20/80 is replaced by the [[Translation (genetics)|translation]] initiation factor [[eIF4E]].<ref>{{cite journal|last1=Maquat|first1=Lynne E.|last2=Tarn|first2=Woan-Yuh|last3=Isken|first3=Olaf|title=The Pioneer Round of Translation: Features and Functions|journal=Cell|date=August 2010|volume=142|issue=3|pages=368–374|doi=10.1016/j.cell.2010.07.022|pmid=20691898|pmc=2950652}}</ref> The eIF4F complex (eIF4E, [[eIF4G]] and [[eIF4A]]) then regulates translation in response to the state of the cell via its [[phosphorylation]] state and again protects the message from decapping.<ref name=Gross2003>{{citation | last1 = Gross | first1 = J.D. | last2 = Moerke | first2 = N.J. | last3 = Von Der Haar | first3 = T. | last4 = Lugovskoy | first4 = A.A. | last5 = Sachs | first5 = A.B. | last6 = McCarthy | first6 = J.E.G. | last7 = Wagner | first7 = G. | year = 2003 | title = Ribosome Loading onto the mRNA Cap is Driven by Conformational Coupling between eIF4G and eIF4E | journal = Cell | volume = 115 | issue = 6 | pages = 739–750 | doi = 10.1016/S0092-8674(03)00975-9 | pmid = 14675538| s2cid = 14728669 | doi-access = free }}</ref>

==Decapping complex==

When translationally repressed or marked for decay by various mechanisms the 5' cap is bound by the mRNA decapping enzyme [[DCP2]]. A host of proteins accompany it including [[UPF1]], [[UPF2]], [[UPF3A]], Dcp1, Dhh1, [[XRN1]], and others. The decapping enzyme removes the 5' cap leading to destruction of the message.<ref name=Parker2007>{{citation | last1 = Parker | first1 = R. | last2 = Sheth | first2 = U. | year = 2007 | title = P Bodies and the Control of mRNA Translation and Degradation | journal = Molecular Cell | volume = 25 | issue = 5 | pages = 635–646 | doi = 10.1016/j.molcel.2007.02.011 | pmid = 17349952| doi-access = free }}</ref>

==References==
{{reflist}}

==External links==
* {{MeshName|nuclear+cap-binding+protein+complex}}

{{RNA-binding proteins}}

[[Category:RNA]]

Cap binding complex - Revision history

imported>Citation bot: Removed proxy/dead URL that duplicated identifier. | Use this bot. Report bugs. | Suggested by SemperIocundus | #UCB_webform 1690/2500