PUM1 is a biphasic negative regulator of innate immunity genes by suppressing LGP2

Area of Science:

• Immunology
• Molecular Biology
• RNA Biology

Background:

• PUM1 (PUF family, RNA binding protein) regulates mRNA stability and function.
• Innate immunity relies on a complex network of gene expression.
• The role of PUM1 in innate immune gene regulation is not fully understood.

Purpose of the Study:

• To investigate the role of PUM1 in regulating innate immunity gene expression.
• To identify specific immune genes regulated by PUM1.
• To elucidate the mechanism by which PUM1 influences innate immune responses.

Main Methods:

• Human cells were transfected with siPUM1 RNA to deplete PUM1.
• Quantitative PCR was used to measure mRNA levels of various immune genes.
• Simultaneous depletion experiments were conducted to assess gene dependencies.
• Interferon-beta (IFNβ) production and its effects were analyzed.
• Herpes Simplex Virus-1 (HSV-1) replication was measured.

Main Results:

• PUM1 depletion led to a cascade of innate immune gene up-regulation, including LGP2, CXCL10, IL6, RIG-I, MDA5, and IFNβ.
• Up-regulation of these genes was dependent on LGP2.
• IFNβ produced after PUM1 depletion enhanced LGP2 and other immune gene expression and reduced HSV-1 replication.
• Not all upregulated genes contained PUM1 binding sites, suggesting mechanisms beyond mRNA stabilization.
• PUM2 depletion did not affect the expression of these innate immune genes.

Conclusions:

• PUM1 acts as a negative regulator of LGP2, a key initiator of innate immunity gene cascades.
• PUM1 controls innate immunity through a regulated, cascading expression of immune genes.
• These findings reveal a novel regulatory mechanism for innate immune responses involving PUM1 and LGP2.