Dbf4-Cdc7 (DDK) Inhibitor PHA-767491 Displays Potent Anti-Proliferative Effects via Crosstalk with the CDK2-RB-E2F
Tekle Pauzaite1, James Tollitt1, Betul Sopaci1
1Biomedical and Life Sciences, Faculty of Health and Medicine, Lancaster University, Lancaster LA1 4YQ, UK.
Biomedicines
|August 26, 2022
Summary
Two DDK inhibitors, PHA-767491 and XL-413, were tested for DNA replication inhibition. PHA-767491 potently inhibits DNA replication initiation and proliferation, unlike XL-413.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Precise regulation of DNA replication initiation involves cyclin-dependent kinases (CDKs) and Dbf4-dependent kinases (DDKs).
- Chemical probes are crucial for studying DDK-mediated regulation of MCM2-7 activation and DNA replication initiation.
Purpose of the Study:
- To assess and compare the inhibitory activities of two DDK inhibitor chemotypes, PHA-767491 and XL-413.
- To elucidate the distinct mechanisms by which these inhibitors affect cellular proliferation, DNA replication initiation, and replisome activity.
Main Methods:
- Cell-free and cell-based proliferation assays were employed.
- Assays included DDK-specific phosphorylation of MCM2, S-phase entry analysis, DNA combing, and DNA replication assays.
- E2F-mediated transcription of G1/S regulators and CDK9 inhibition were also investigated.
Main Results:
- Both PHA-767491 and XL-413 reduced DDK-specific MCM2 phosphorylation but exhibited differential potency in preventing S-phase entry.
- PHA-767491 demonstrated potent inhibition of DNA replication initiation, whereas XL-413 showed weak activity.
- PHA-767491 decreased E2F-mediated transcription of cyclin A2, cyclin E1, and cyclin E2, independent of CDK9 inhibition.
Conclusions:
- PHA-767491 is a potent inhibitor of DNA replication initiation and exhibits enhanced anti-proliferative effects.
- PHA-767491's efficacy is attributed to its dual inhibition of DDK and the CDK2-Rb-E2F transcriptional network.
- These findings provide a molecular basis for PHA-767491's increased anti-proliferative effects in RB+ cancer cell lines.
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