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Revisiting the evolution of the yeast Atg1 complex
Kha M Nguyen1, Hannah R Shariati1, Calvin K Yip1
1Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada.
Autophagy Reports
|October 2, 2025
Summary
The yeast Atg1 complex evolved differently between budding and fission yeasts. Budding yeasts with Atg101 show a rod-shaped Atg17 scaffold, suggesting alternative evolutionary paths for autophagy-related proteins.
Area of Science:
- Molecular and Cellular Biology
- Evolutionary Biology
- Yeast Genetics
Background:
- The autophagy-related (ATG) protein complex, specifically Atg1, is crucial for initiating nonselective autophagy in yeast.
- Distinct compositions of the Atg1 complex exist between budding yeast (Saccharomyces cerevisiae) and fission yeast (Schizosaccharomyces pombe), with differing scaffold proteins (Atg17, Atg29, Atg31 vs. Atg17, Atg101).
- The evolutionary timeline and structural impact of these compositional differences on Atg17 remain largely unknown.
Purpose of the Study:
- To investigate the evolutionary divergence of the Atg1 complex in yeast.
- To determine the structural variations in the Atg17 scaffold across different yeast species.
- To explore the potential functional implications of Atg101 incorporation and the Atg13 HORMA domain.
Main Methods:
- Systematic composition analysis of the Atg1 complex across various yeast species.
- Structural modeling and negative stain electron microscopy (EM) for scaffold structure determination.
- Analysis of the Atg13 HORMA domain in Schizosaccharomyces pombe.
Main Results:
- Atg101 was identified in the Atg1 complex of several budding yeast species, with some co-occurring with Atg29/Atg31.
- Budding yeast species possessing Atg101 exhibited a rod-shaped Atg17 scaffold, contrasting with the S-shaped scaffold in species lacking Atg101.
- The Atg13 HORMA domain in Schizosaccharomyces pombe may have a stabilizing cap, hinting at a distinct role for Atg101.
Conclusions:
- The presence of Atg101 correlates with a rod-shaped Atg17 structure in budding yeasts, indicating a significant evolutionary shift.
- These findings suggest alternative evolutionary pathways for the Atg1 complex structure and function within the yeast lineage.
- The study delineates potential evolutionary trajectories for the core autophagy initiation complex.
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