Identification of Target Genes for the Tumor Suppressor RIZ1 Using Gene Expression Profiling.
Bibliographic record
Abstract
Abstract RIZ1 (PRDM2) is a tumor suppressor gene on 1p36 that frequently undergoes deletion, rearrangements, and loss of heterozygosity in a broad spectrum of tumors. RIZ1 is a member of the nuclear protein methyltransferase superfamily involved in chromatin remodeling. RIZ1 contains a ~130 amino acid conserved domain (PR or SET) that is important in chromatin-mediated regulation of gene expression and in the development of cancer. RIZ1 methylates Histone H3 on K9 and this activity may play a role in transcription repression as H3-K9 methylation is known to be associated with repression. Aberrant activities or mistargeting of chromatin modifying activities are proving to have unexpected links to cancer. We and others have shown that RIZ1 expression is down regulated in human leukemias and in the human erythroleukemia cell line K562. Expression of RIZ1 in K562 reduced proliferation, increased apoptosis, and promoted erythroid differentiation. To understand how RIZ1’s DNA binding, methyltransferase, and transcription repressor functions are related to its tumor suppressor activity it is necessary to characterize RIZ1 target genes. We used DNA microarrays to globally monitor how RIZ1 affects gene expression profiles. We constructed a K562 cell line with RIZ1 stably integrated under the control of a CMV promoter and analyzed the gene expression profiles of K652 and K562 + RIZ1 using a 42K Stanford human gene microarray. By comparing the gene expression profiles of these cell lines, we identified potential RIZ1 gene targets that are up and down regulated in the presence of RIZ1. In total, we identified 5 upregulated genes and 20 down regulated genes using significance analysis of microarrays (SAM) and standard deviation filter analysis of the gene expression data. RIZ1-mediated changes in gene expression profiling indicate that RIZ1 is potentially involved in the regulation and connection of the IGF-1 (IGF-1, IGFBP2) and integrin (LMS1) pathways, and in the activation of the TGF-β (SPARC) pathway. The genes perturbed by RIZ1 expression suggest that the tumor suppressor properties of RIZ1 arise from its control of proliferation, apoptosis and differentiation using these pathways. Finally, we observed an overrepresentation of the SP-1 transcription factor binding sites in genes that are upregulated in the absence of RIZ1. This correlates with the ability of RIZ1 to recognize SP1 sequences.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".