mRNA export through an additional cap-binding complex consisting of NCBP1 and NCBP3

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• The flow of genetic information relies on messenger RNA (mRNA) processing, which is initiated by a 5'-cap modification.
• The canonical cap-binding complex (CBC), comprising NCBP1 and NCBP2, is thought to regulate all capped RNA molecules.
• The precise roles of individual CBC components in mRNA export and cellular viability remain incompletely understood.

Purpose of the Study:

• To investigate the specific functions of NCBP1 and NCBP2 in RNA processing and export.
• To identify novel cap-binding proteins involved in mRNA biogenesis.
• To elucidate the role of alternative cap-binding complexes in cellular responses to stress.

Main Methods:

• RNA immunoprecipitation assays
• CRISPR-Cas9 gene editing
• Western blotting
• Analysis of poly(A) RNA export

Main Results:

• NCBP1, but not NCBP2, is essential for cell viability and poly(A) RNA export.
• C17orf85, renamed NCBP3, forms an alternative cap-binding complex (CBC) with NCBP1 in higher eukaryotes.
• This NCBP1-NCBP3 complex binds mRNA, interacts with mRNA processing factors, and facilitates poly(A) RNA export.
• NCBP2 can compensate for NCBP3 loss under normal conditions, but NCBP3 is critical during stress, such as viral infection.

Conclusions:

• An alternative cap-binding complex (CBC) composed of NCBP1 and NCBP3 exists and plays a vital role in mRNA biogenesis.
• This alternative CBC is particularly important for cellular resilience under stress conditions.
• The findings reveal a more complex regulatory network for mRNA processing and export than previously appreciated.