What complex binds to the 5' cap of mature mRNA for export?

The CAP Binding Complex is crucial for the export of mature mRNA from the nucleus to the cytoplasm. The 5' cap is a specially modified guanine nucleotide added to the beginning of the mRNA transcript. This cap not only protects the mRNA from degradation but also plays a vital role in ribosome recognition during translation initiation.

The CAP Binding Complex binds specifically to this 5' cap structure, facilitating the interaction of the mRNA with other export factors and ensuring its proper delivery across the nuclear membrane. This complex is essential for recognizing the mRNA as mature, which is necessary because only fully processed mRNAs are exported and utilized in protein synthesis.

Other options, such as the Exon Junction Complex, Poly-A Binding Proteins, and Initiation Factors, play roles in different aspects of mRNA processing and translation. The Exon Junction Complex is involved in ensuring the mRNA has been spliced correctly, Poly-A Binding Proteins interact with the poly-A tail to stabilize the mRNA and aid in translation, whereas Initiation Factors are critical for starting the translation process but are not directly involved in the export of mRNA. Overall, the CAP Binding Complex is the key player in the export of mature mRNA due to its specific binding to