Cap binding complex

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

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 CBP20/CBP80 in metazoans.

They also serve as a marker for the so-called pioneer round of translation when the message is examined by nonsense mediated decay.

[3] When translationally repressed or marked for decay by various mechanisms the 5' cap is bound by the mRNA decapping enzyme DCP2.

The decapping enzyme removes the 5' cap leading to destruction of the message.

Surface model of the cap-binding complex (heavy chain pink, light chain yellow, m7G and GDP as balls), after PDB 1H2T.