Exonjunctionkomplexet

Exonjunctionkomplexet, often referred to as the exon junction complex (EJC) in English, is a multiprotein complex that plays a crucial role in post-transcriptional gene regulation in eukaryotes. It is deposited onto messenger RNA (mRNA) during the process of RNA splicing, specifically at the boundary between exons after an intron has been removed. The EJC is a dynamic entity that can associate with and dissociate from the mRNA molecule at various stages of its life cycle.

The primary function of the EJC is to mark the exon-exon junctions. This marking serves several important purposes. One key role is in nonsense-mediated decay (NMD), a surveillance pathway that degrades aberrant mRNAs containing premature termination codons. The presence of the EJC downstream of a stop codon signals that the mRNA is likely correctly spliced and therefore not targeted for degradation. Conversely, if a stop codon is found upstream of an EJC, it indicates a potential problem, triggering NMD.

Beyond mRNA surveillance, the EJC also influences mRNA export from the nucleus to the cytoplasm and is involved in regulating mRNA translation. It can interact with other proteins that are important for these processes, thereby controlling the efficiency and localization of protein synthesis. Furthermore, the EJC has been implicated in gene expression regulation during embryonic development. Its components are conserved across many eukaryotic species, highlighting its fundamental importance in gene expression.