Functional Analysis of Aberrant CIZ1 Forms in Cancer
Bibliographic record
Abstract
Cip1-interacting zinc finger protein 1 (CIZ1) is a nuclear matrix protein that forms large sub-nuclear assemblies at the inactive X chromosome (Xi) in females, and smaller assemblies throughout the nucleus in males and females.CIZ1 is linked with maintenance of histone modifications that specify facultative heterochromatin, and is extensively mis-expressed in human cancers, including under-expression, overexpression, and mis-splicing events.Here, I describe uncoupled expression of the CIZ1 N-terminal replication domain and Cterminal anchor domain (AD), leading to over-expression of AD amplicons in breast cancer and derived cell lines.Modelling over-expression of the AD in murine cells led to observed dispersal of endogenous CIZ1 assemblies at the Xi.Therefore, AD fragments appear to have dominant negative (DN) activity, and these DN effects coincide with H2AK119ub1 and H3K27me3 loss from Xi chromatin.Further analysis revealed that DN effects occur in early G1, when new CIZ1 assemblies normally reform at the Xi after mitosis.A mutagenesis screen identified the matrin 3homology domain as important for the DN effect on endogenous CIZ1 assemblies, and for stable self-interaction to form a homo-dimeric complex in vitro, suggesting that DN interference involves disruption of CIZ1 dimers.Additionally, I investigated the CIZ1B variant that is prevalent in lung cancer.I show that exclusion of part of the acidic domain in CIZ1B does not influence dimerisation.However, a mass spectrometry interaction study revealed increased and decreased affinity for protein interaction partners in the C-terminus of CIZ1B compared to wild-type, most notably CIZ1B had a reduced ability to bind to linker histones and DNA damage response associated proteins.These observations suggest that CIZ1 could be implicated in mechanisms for protection of the genome and epigenome, and that aberrant expression of CIZ1 in early-stage cancers could therefore contribute to genome-wide loosening of gene repression, and a move toward epigenetic decay.
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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 | 0.000 |
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".