Cap binding complex

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The 5' cap of eukaryotic messenger RNA is bound at all times by various Cap-binding complexes.

Nuclear cap-binding complex[edit]

In the nucleus freshly transcribed mRNA molecules are bound on the 5' cap by the nuclear cap-binding complex of Cbc1/Cbc2 in yeast or CBC20/CBC80 in metazoans. These aid in the export of the mRNA and protect it from decapping. They also serve as a marker for the so-called pioneer round of translation when the message is examined by nonsense mediated decay.[1]

Cytoplasmic cap-binding complex[edit]

After the first round of translation the nuclear complex is replaced by the translation initiation factors eIF-4E and eIF-4G. These regulate translation in response to the state of the cell via their phosphorylation state and again protect the message from decapping.[2]

Decapping complex[edit]

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.[3]

References[edit]

  1. ^ Isken, O.; Maquat, L.E. (2007), "Quality control of eukaryotic mRNA: safeguarding cells from abnormal mRNA function", Genes & Development 21 (15): 1833, doi:10.1101/gad.1566807, PMID 17671086 
  2. ^ Gross, J.D.; Moerke, N.J.; Von Der Haar, T.; Lugovskoy, A.A.; Sachs, A.B.; McCarthy, J.E.G.; Wagner, G. (2003), "Ribosome Loading onto the mRNA Cap is Driven by Conformational Coupling between eIF4G and eIF4E", Cell 115 (6): 739–750, doi:10.1016/S0092-8674(03)00975-9, PMID 14675538 
  3. ^ Parker, R.; Sheth, U. (2007), "P Bodies and the Control of mRNA Translation and Degradation", Molecular Cell 25 (5): 635–646, doi:10.1016/j.molcel.2007.02.011, PMID 17349952 

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