Cytoplasmic mRNA decay controlling inflammatory gene expression is determined by pre-mRNA fate decision

Area of Science:

• Molecular Biology
• Immunology
• Gene Regulation

Background:

• Immune response fidelity relies on controlled mRNA degradation, primarily mediated by RNA-binding proteins (RBPs).
• The precise mechanisms governing selective mRNA degradation remain largely unknown, with questions about stochastic versus directed processes.

Purpose of the Study:

• To elucidate the molecular mechanisms by which tristetraprolin (TTP), an anti-inflammatory RBP, regulates mRNA degradation.
• To determine whether TTP targets pre-mRNA or mature mRNA for degradation and the implications for cellular regulation.

Main Methods:

• Utilized human and mouse cell lines to investigate TTP-mediated mRNA destabilization.
• Analyzed the role of TTP-RNA interactions in forming molecular assemblies for mRNA degradation.
• Investigated the subcellular localization of TTP activity, specifically focusing on nuclear versus cytoplasmic events.

Main Results:

• TTP destabilizes target mRNAs through a hierarchical molecular assembly dependent on TTP-RNA interactions.
• The TTP homolog ZFP36L1 demonstrates similar regulatory requirements, suggesting a conserved mechanism.
• Crucially, TTP binding to pre-mRNA in the nucleus licenses the formation of cytoplasmic mRNA-destabilization complexes, identifying pre-mRNA as the primary target.

Conclusions:

• The fate of inflammation-induced mRNAs is determined during their synthesis in the nucleus through TTP binding to pre-mRNA.
• This nuclear-initiated mechanism effectively prevents the translation of excessive inflammatory mediators, ensuring immune response control.
• The findings reveal a novel regulatory checkpoint at the pre-mRNA level controlling gene expression and inflammatory responses.