A Toll-dependent Bre1/Rad6-cact feedback loop in controlling host innate immune response

Area of Science:

• Molecular Biology
• Immunology
• Genetics

Background:

• The Toll signaling pathway regulates embryogenesis and innate immunity in eukaryotes.
• In flies, cactus is a key negative regulator of Toll immune responses.
• Toll pathway activation during immune defense also induces cactus expression.

Purpose of the Study:

• To investigate the mechanisms behind the dual role of the Toll pathway.
• To elucidate how pathogenic stimuli regulate the Toll pathway and cactus expression.

Main Methods:

• Investigated the induction of E3 ligase Bre1 by the transcription factor dorsal upon pathogenic stimuli.
• Examined the complex formation between Bre1 and E2 Rad6.
• Assessed the mono-ubiquitination of histone H2B and its effect on cactus transcription.

Main Results:

• Pathogenic stimuli induce dorsal, which in turn upregulates the E3 ligase Bre1.
• Bre1, complexed with E2 Rad6, mono-ubiquitinates histone H2B.
• This process promotes cactus transcription, contributing to Toll immune response homeostasis.

Conclusions:

• A novel Toll signal-dependent regulatory mechanism governing the Toll pathway in Drosophila has been characterized.
• This machinery involves Bre1-mediated histone modification to control cactus expression and maintain immune homeostasis.