Theresa Zeisner
@theresazeisner.bsky.social
PostDoc in the Pauli lab at the IMP, Vienna. Interested in proteostasis during early development 🧬🔬
Big thanks to Tania for her phospho-expertise and the entire Nurse lab (past and present) for their support, comments and discussions! 🌟
February 24, 2025 at 5:09 PM
Big thanks to Tania for her phospho-expertise and the entire Nurse lab (past and present) for their support, comments and discussions! 🌟
Without PP2A-B55 or CDC14 cells enter mitosis earlier
This advance is independent of CDK activity regulation. This indicates that in the absence of these Ppases, critical CDK substrates can be phosphorylated at lower CDK activity levels (ie earlier), thus advancing mitotic entry.
This advance is independent of CDK activity regulation. This indicates that in the absence of these Ppases, critical CDK substrates can be phosphorylated at lower CDK activity levels (ie earlier), thus advancing mitotic entry.
February 24, 2025 at 5:09 PM
Without PP2A-B55 or CDC14 cells enter mitosis earlier
This advance is independent of CDK activity regulation. This indicates that in the absence of these Ppases, critical CDK substrates can be phosphorylated at lower CDK activity levels (ie earlier), thus advancing mitotic entry.
This advance is independent of CDK activity regulation. This indicates that in the absence of these Ppases, critical CDK substrates can be phosphorylated at lower CDK activity levels (ie earlier), thus advancing mitotic entry.
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.
Using a fluorescent sensor, we showed that without PP2A-B55, a candidate substrate (Cut3-T19) is phosphorylated earlier and less rapidly.
February 24, 2025 at 5:09 PM
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.
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.
February 24, 2025 at 5:09 PM
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.
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.
February 24, 2025 at 5:09 PM
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.
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.
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.
February 24, 2025 at 5:09 PM
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.
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
• 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
February 24, 2025 at 5:09 PM
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
• 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.
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.
February 24, 2025 at 5:09 PM
🔎 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.
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.
❓Open questions
How do CDK-opposing Ppases (PP2A-B55, PP2A-B56, PP1 & CDC14) together influence the phosphorylation timing of CDK substrates?
To answer this, we first needed to identify which CDK substrate is targeted by which Ppase.
How do CDK-opposing Ppases (PP2A-B55, PP2A-B56, PP1 & CDC14) together influence the phosphorylation timing of CDK substrates?
To answer this, we first needed to identify which CDK substrate is targeted by which Ppase.
February 24, 2025 at 5:09 PM
❓Open questions
How do CDK-opposing Ppases (PP2A-B55, PP2A-B56, PP1 & CDC14) together influence the phosphorylation timing of CDK substrates?
To answer this, we first needed to identify which CDK substrate is targeted by which Ppase.
How do CDK-opposing Ppases (PP2A-B55, PP2A-B56, PP1 & CDC14) together influence the phosphorylation timing of CDK substrates?
To answer this, we first needed to identify which CDK substrate is targeted by which Ppase.
🔄 CDK-opposing Ppases
• Important at mitotic exit to dephosphorylate CDK substrates
• Ppases are also active during interphase ➡️ could affect phosphorylation timing
• But for the majority of CDK substrate sites, it is not known which Ppase targets it
• Important at mitotic exit to dephosphorylate CDK substrates
• Ppases are also active during interphase ➡️ could affect phosphorylation timing
• But for the majority of CDK substrate sites, it is not known which Ppase targets it
February 24, 2025 at 5:09 PM
🔄 CDK-opposing Ppases
• Important at mitotic exit to dephosphorylate CDK substrates
• Ppases are also active during interphase ➡️ could affect phosphorylation timing
• But for the majority of CDK substrate sites, it is not known which Ppase targets it
• Important at mitotic exit to dephosphorylate CDK substrates
• Ppases are also active during interphase ➡️ could affect phosphorylation timing
• But for the majority of CDK substrate sites, it is not known which Ppase targets it
⏰ The cell cycle is driven by reversible phosphorylations
Hundreds of proteins need to be phosphorylated at the right time by cyclin-dependent kinases (CDKs) to order cell cycle events. These phosphorylations are opposed by phosphatases (Ppases), such as PP2A-B55, PP2A-B56, PP1 & CDC14.
Hundreds of proteins need to be phosphorylated at the right time by cyclin-dependent kinases (CDKs) to order cell cycle events. These phosphorylations are opposed by phosphatases (Ppases), such as PP2A-B55, PP2A-B56, PP1 & CDC14.
February 24, 2025 at 5:09 PM
⏰ The cell cycle is driven by reversible phosphorylations
Hundreds of proteins need to be phosphorylated at the right time by cyclin-dependent kinases (CDKs) to order cell cycle events. These phosphorylations are opposed by phosphatases (Ppases), such as PP2A-B55, PP2A-B56, PP1 & CDC14.
Hundreds of proteins need to be phosphorylated at the right time by cyclin-dependent kinases (CDKs) to order cell cycle events. These phosphorylations are opposed by phosphatases (Ppases), such as PP2A-B55, PP2A-B56, PP1 & CDC14.