Comparative genetic analysis of PP2A-Cdc55 regulators in budding yeast

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Cdc55, a regulatory subunit of protein phosphatase 2A (PP2A), is crucial for mitotic progression.
• In budding yeast, Zds1 and Zds2 proteins sequester Cdc55 from the nucleus, promoting Cdk1 activation.
• Higher eukaryotes utilize conserved ENSA/ARPP-19 proteins to inhibit PP2A-B55 during mitotic entry.

Purpose of the Study:

• To compare the roles of Zds1/Zds2 and Igo1/Igo2 in regulating Cdc55 during budding yeast mitosis.
• To investigate the distinct mechanisms and evolutionary conservation of PP2A-Cdc55 regulation.

Main Methods:

• Comparative analysis of Zds1/Zds2 and Igo1/Igo2 functions in budding yeast.
• Localization studies of Igo1 and Zds1 within yeast cells.
• Functional assays to assess the impact on Cdc55 activity and mitotic progression.

Main Results:

• Igo1/Igo2 inhibit Cdc55 in early mitosis, but their contribution is less significant than Zds1/Zds2.
• Igo1 localizes to the nucleus, unlike Zds1 which is cytoplasmic and at cell polarity sites.
• This suggests distinct mechanisms of PP2A-Cdc55 inhibition by Zds1/Zds2 and Igo1/Igo2.

Conclusions:

• ENSA-family proteins (Igo1/Igo2) have an evolutionarily conserved role in inhibiting PP2A-Cdc55.
• Zds1-mediated nuclear sequestration of PP2A-Cdc55 is a unique mechanism for closed mitosis in fungi.
• Distinct regulatory strategies for PP2A-Cdc55 exist between fungi and higher eukaryotes.