Cap binding complex

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

1 Nuclear cap-binding complex
2 Cytoplasmic cap-binding complex
3 Decapping complex
4 References
5 External links

Nuclear cap-binding complex

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

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

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

^ 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, http://www.genesdev.org/cgi/content/full/21/15/1833
^ 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, http://www.cell.com/cgi/content/full/115/6/739
^ 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, http://linkinghub.elsevier.com/retrieve/pii/S1097276507001116

External links

MeSH nuclear+cap-binding+protein+complex

Carrier proteins, Nucleoprotein: RNA-binding protein

Butyrate response factor 1 • Fragile X mental retardation protein • Rev • hu paraneoplastic encephalomyelitis antigens • mRNA cleavage and polyadenylation factors (Cleavage and polyadenylation specificity factor, Cleavage stimulation factor) • host factor 1 protein • Aconitase (ACO1, ACO2) • nuclear factor 90 proteins (ILF2) • Poly(A)-binding protein (PABPC1, PABPC3, PABPC4) • polypyrimidine tract-binding protein • ribonucleoprotein • RNA cap-binding protein (Cap binding complex, EIF4E, EIF4G1) • SMN complex proteins (SMN1, SMN2, DDX20)

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°)