What happens in the absence of the Ppases?

Using a fluorescent sensor, we showed that without PP2A-B55, a candidate substrate (Cut3-T19) is phosphorylated earlier and less rapidly.

This suggests that the identity of the Ppase that targets a CDK substrate site affects its phosphorylation timing. The exact phosphorylation timing of a given site is determined by a combination of factors.

Does the division of labour between the Ppase impact the timing of CDK substrate phosphorylation? Yes! ✅

Phosphoproteomic timecourse showed that CDK substrates targeted by CDC14 and PP2A-B56 are, on average, net phosphorylated first, followed by CDK substrates targeted by PP1 and then PP2A-B55.

Identifying some more Ppase substrates…

We also identified 3,000+ Ppase substrates phosphorylated by other kinases (not CDK). The identified Ppase motifs were similar to those identified in other eukaryotes, indicating conservation of Ppase substrate specificity.

Distinct Ppase targets

• PP2A-B55, B56, CDC14 & PP1 targeted specific subgroups of CDK sites
• <5% of sites were targeted by multiple Ppases
• Ppases had different preferences for amino acids

🔎 Identifying Ppase substrates

We used phosphoproteomics: inhibiting CDK with & without Ppase and tracking dephosphorylation. We classified a site as a Ppase substrate if it was dephosphorylated substantially slower in the absence of the Ppase.

🚨New preprint🚨

How do phosphatases affect CDK substrate phosphorylation timing during the cell cycle?

We showed that substrates dephosphorylated by different Ppases are net phosphorylated at different times.

📖 Read here: doi.org/10.1101/2025... & follow along for some key insights 🧵