CD95/Fas ligand mRNA is toxic to cells

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• CD95/Fas ligand (CD95L) binding to its receptor CD95 triggers apoptosis.
• Previous work showed CD95L-derived si/shRNAs effectively kill cancer cells by targeting survival genes.
• The direct role of full-length CD95L mRNA in cell death remained unexplored.

Purpose of the Study:

• To investigate the toxicity of full-length CD95L mRNA and its mechanism of cell death induction.
• To determine if CD95L mRNA is processed into small RNAs (sRNAs) and loaded into the RNA induced silencing complex (RISC).
• To explore the potential for endogenous genes to be processed into sRNAs for cell fate regulation.

Main Methods:

• Expression of full-length CD95L mRNA in cells.
• Analysis of sRNA generation from CD95L mRNA.
• Assessment of sRNA loading into RISC.
• Investigation of Dicer and Drosha independence in CD95L processing.
• Examination of endogenous gene processing into sRNAs.

Main Results:

• Full-length CD95L mRNA expression is toxic and induces a cell death pathway similar to apoptosis.
• CD95L-derived sRNAs are generated and loaded into RISC, mediating the observed toxicity.
• CD95L mRNA processing into sRNAs occurs independently of Dicer and Drosha.
• Endogenous protein-coding genes, especially those regulating translation, can also be processed into sRNAs and loaded into RISC.

Conclusions:

• Full-length CD95L mRNA itself possesses potent cytotoxic properties, inducing cell death through an RNAi-dependent mechanism.
• The processing of CD95L mRNA into toxic sRNAs bypasses canonical Dicer/Drosha pathways, highlighting an alternative RNAi route.
• This study reveals a novel layer of cell fate regulation where CD95L and potentially other endogenous mRNAs are processed into sRNAs that modulate cellular processes via RISC.