Promoter Methylation Regulates SAMHD1 Gene Expression in Human CD4+ T Cells
Bibliographic record
Abstract
The retrovirus restriction factor SAMHD1 is the first identified mammalian dNTP triphosphohydrolase that is highly expressed in human myeloid lineage cells and CD4(+) T lymphocytes. Although SAMHD1 expression is variable in human cell lines and tissue types, mechanisms underlying SAMHD1 gene regulation have not been defined. Recent studies showed that SAMHD1 is highly expressed in human primary CD4(+) T lymphocytes, but not in some CD4(+) T cell lines. Here, we report that SAMHD1 expression varies among four CD4(+) T cell lines and is transcriptionally regulated. Cloning and sequence analysis of the human SAMHD1 promoter revealed a CpG island that is methylated in CD4(+) T cell lines (such as Jurkat and Sup-T1), resulting in transcriptional repression of SAMHD1. We also found that the SAMHD1 promoter is unmethylated in primary CD4(+) T lymphocytes, which express high levels of SAMHD1, indicating a direct correlation between the methylation of the SAMHD1 promoter and transcriptional repression. SAMHD1 expression was induced in CD4(+) T cell lines by blocking DNA methyltransferase activity, suggesting that promoter methylation is one of the key epigenetic mechanisms by which SAMHD1 expression is regulated.
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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) | 0.002 | 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".