Exon junction complex

The EJC consists of a stable heterotetramer core, which serves as a binding platform for other factors necessary for the mRNA pathway.

[3] The binding of these proteins to nuclear speckled domains has been measured recently and it may be regulated by PI3K/AKT/mTOR signaling pathways.

[11][12] The protein component Magoh is thought to facilitate the subcytoplasmic localization of mRNAs while Aly is engaged in nuclear mRNA export.

[16] UAP56 is recognized as an RNA helicase but acts as a splicing factor required for early spliceosome assembly.

This component is known to take part in a variety of functions ranging from splicing to transcriptional regulation and chromatin structure.

[26][27] The binding of the EJC to the mRNA occurs in a sequence independent manner, to form the mature messenger ribonucleoprotein (mRNP).

In order for the translocation of mRNAs through the nuclear pore complex to occur, a heterodimer consisting of NXF1/TAP and NXT1/p15 must bind to the transcripts.

[citation needed] Exon junction complexes play a major role in mRNA surveillance.

More specifically, they are found in the nonsense mediated decay pathway (NMD), wherein mRNA transcripts with premature stop codons are degraded.

In normal mRNA translation, the ribosome binds to the transcript and begins amino acid chain elongation.

The EJC protein MAGOH, Y14 and eIF4AIII provide a binding for UPF3, which acts as a bridge between UPF2 and UPF1 forming a trimeric complex.

[33] The EJC core stably anchors the UPF complex to the mRNA, and aids in regulation of essential UPF1 protein.