A molecular function of Zillion Different Screens protein explained

In a recent paper in Journal of Cell Biology entitled “Spatial regulation of Cdc55-PP2A by Zds1/Zds2 controls mitotic entry and mitotic exit in budding yeast“, Brandeis postdoctoral fellow Valentina Rossio and Assistant Professor of Biology Satoshi Yoshida reveal a molecular function of a mysterious protein Zds1.

The Zds1 protein in yeast¬† was identified some years ago in “a zillion different screens” for cell cycle mutants, stress response mutants, RNA metabolism mutants, etc., but the molecular function of the protein remained a mystery for more than 15 years. Rossio revealed that Zds1’s key target is a protein phosphatase 2A (PP2A) complex. She showed that Zds1 controls nucleocytoplasmic distribution of PP2A complex, and that this regulation is critical for cells to know when to enter and to exit from mitosis (picture below; cells lacking Zds proteins adopt an abnormal shape because of problems in mitosis). Rossio thinks all the other complicated phenotypes associated with ZDS1 can also be explained by PP2A regulation and is currently studying mechanistic details about the Zds1-PP2A interaction.

See also the accompanying commentary “Proteins keep Cdc55 in its place

Cell cycle checkpoint from the stringent response

E.coli cells exiting the stringent response

E.coli cells exiting the stringent response

The stringent response in E.coli is a response to nutrient (typically amino acid) starvation and is characterized by the accumulation of the small molecular regulator ppGpp, and a global response in transcriptional regulation.  In a new paper in PLoS Genetics, Daniel Ferullo and Susan Lovett examine chromosome segregation during the stringent respons and discuss what appears to be a novel G1-like cell cycle checkpoint in bacteria that occurs as the result.

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