Dbf4 and Cdc7 Proteins Promote DNA Replication through Interactions with Distinct Mcm2–7 Protein Subunits
Bibliographic record
Abstract
The essential cell cycle target of the Dbf4/Cdc7 kinase (DDK) is the Mcm2–7 helicase complex. Although Mcm4 has been identified as the critical DDK phosphorylation target for DNA replication, it is not well understood which of the six Mcm2–7 subunits actually mediate(s) docking of this kinase complex. We systematically examined the interaction between each Mcm2–7 subunit with Dbf4 and Cdc7 through two-hybrid and co-immunoprecipitation analyses. Strikingly different binding patterns were observed, as Dbf4 interacted most strongly with Mcm2, whereas Cdc7 displayed association with both Mcm4 and Mcm5. We identified an N-terminal Mcm2 region required for interaction with Dbf4. Cells expressing either an Mcm2 mutant lacking this docking domain (Mcm2ΔDDD) or an Mcm4 mutant lacking a previously identified DDK docking domain (Mcm4ΔDDD) displayed modest DNA replication and growth defects. In contrast, combining these two mutations resulted in synthetic lethality, suggesting that Mcm2 and Mcm4 play overlapping roles in the association of DDK with MCM rings at replication origins. Consistent with this model, growth inhibition could be induced in Mcm4ΔDDD cells through Mcm2 overexpression as a means of titrating the Dbf4-MCM ring interaction. This growth inhibition was exacerbated by exposing the cells to either hydroxyurea or methyl methanesulfonate, lending support for a DDK role in stabilizing or restarting replication forks under S phase checkpoint conditions. Finally, constitutive overexpression of each individual MCM subunit was examined, and genotoxic sensitivity was found to be specific to Mcm2 or Mcm4 overexpression, further pointing to the importance of the DDK-MCM ring interaction. Background: Dbf4/Cdc7 triggers DNA replication by phosphorylating Mcm2–7 helicase. Results: Disruption of both the Dbf4-Mcm2 and Cdc7-Mcm4 interactions results in growth inhibition and sensitivity to genotoxic stress. Conclusion: Functionally overlapping Dbf4-Mcm2 and Cdc7-Mcm4 interactions promote DNA replication and resistance to fork inhibition. Significance: Characterizing how Dbf4/Cdc7 interacts with the Mcm2–7 ring is crucial to understanding the regulation of DNA replication.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".