Dimerization of CtIP, a BRCA1- and CtBP-interacting Protein, Is Mediated by an N-terminal Coiled-coil Motif
Bibliographic record
Abstract
CtIP is a transcriptional co-regulator that binds a number of proteins involved in cell cycle control and cell development, such as CtBP (C terminus-binding protein), BRCA1 (breast cancer-associated protein-1), and LMO4 (LIM-only protein-4). The only recognizable structural motifs within CtIP are two putative coiled-coil domains located near the N and C termini of the protein. We now show that the N-terminal coiled coil (residues 45-160), but not the C-terminal coiled coil, mediates homodimerization of CtIP in mammalian 293T cells. The N-terminal coiled coil did not facilitate binding to LMO4 and BRCA1 proteins in these cells. A protease-resistant domain (residues 27-168) that minimally encompasses the putative N-terminal coiled coil was identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. This region is predicted to contain two smaller coiled-coil regions. The CtIP-(45-160) dimerization domain is helical and dimeric, indicating that the domain does form a coiled coil. The two smaller domains, CtIP-(45-92) and CtIP-(93-160), also formed dimers of lower binding affinity, but with less helical content than the longer peptide. The hydrodynamic radius of CtIP-(45-160) is the same as those of CtIP-(45-92) and CtIP-(93-160), implying that CtIP-(45-160) does not form a single long coiled coil, but a more compact structure involving homodimerization of the two smaller coiled coils, which fold back as a four-helix bundle or other compact structure. These results suggest a specific model for CtIP homodimerization via its N terminus and contribute to an improved understanding of how this protein might assemble other factors required for its role as a transcriptional corepressor.
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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) | 0.000 | 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 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".