Distinct Domains Contribute to the Subcellular Localization of Human cGAS in Yeast

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Cyclic GMP-AMP synthase (cGAS) is a key cytoplasmic DNA sensor initiating immune responses.
• cGAS localization, including nuclear translocation, is critical for its regulation and catalytic activity.
• Understanding cGAS subcellular localization is essential for deciphering its immune signaling pathways.

Purpose of the Study:

• To investigate the subcellular localization of cGAS using heterologous expression in Saccharomyces cerevisiae.
• To identify domains and motifs within cGAS that regulate its localization and aggregation.
• To establish yeast as a model system for studying cGAS localization dynamics.

Main Methods:

• Heterologous expression of cGAS fused to eGFP in Saccharomyces cerevisiae.
• Microscopy to observe cGAS-eGFP localization patterns within yeast cells.
• Analysis of cGAS localization upon deletion of its N-terminus and mutation of the DNA-binding motif.

Main Results:

• cGAS-eGFP predominantly localized to aggregates at the endoplasmic reticulum-mitochondria encounter structure (ERMES) and juxtanuclear protein quality compartments (JUNQs).
• Deletion of the cGAS N-terminus promoted nuclear localization and reduced cytoplasmic aggregates.
• A mutation in the DNA-binding motif also increased nuclear localization of cGAS.

Conclusions:

• Both the N-terminal and C-terminal domains of cGAS collaborate to restrict nuclear entry and maintain cytoplasmic pools.
• Heterologous cGAS expression in yeast provides a valuable model for studying its subcellular localization and aggregation.
• These findings offer insights into the regulatory mechanisms governing cGAS localization and function.