RNA binding by ADARs prevents RNA interference from attacking self-produced dsRNA

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• Organisms distinguish self from foreign RNA to regulate immune responses and avoid autoimmunity.
• Double-stranded RNA (dsRNA) is a key trigger for immune responses, but also present in host cells.
• A-to-I RNA editing (by ADARs) and RNA interference (RNAi) are critical host pathways for dsRNA regulation and gene expression.

Purpose of the Study:

• Investigate the interplay between ADARs and RNAi in regulating dsRNA.
• Determine how ADARs prevent the immune system from targeting self-RNA.
• Examine the role of ADARs in preventing exogenous RNAi in vivo.

Main Methods:

• Studied siRNA structure and quantity at RNA editing sites in the model organism Caenorhabditis elegans.
• Utilized ADAR mutant animals to assess the impact on siRNA generation.
• Investigated the ability of ADARs to prevent exogenous RNAi in vivo.

Main Results:

• ADAR mutants showed significantly increased siRNAs targeting edited genes.
• ADARs antagonize the initial step of RNAi processing, preventing primary siRNA generation from editing sites.
• ADARs interfere with exogenous RNAi efficacy, likely to prevent trans-silencing, with ADR-2 binding implicated.

Conclusions:

• ADARs play a crucial role in protecting self-produced dsRNA from aberrant immune recognition.
• The RNA editing process, mediated by ADARs, prevents self-RNA from triggering unnecessary immune responses.
• ADARs act as a critical checkpoint, differentiating self-dsRNA from foreign dsRNA to maintain homeostasis.