Genetic diversity at the UGT1 locus is amplified by a novel 3′ alternative splicing mechanism leading to nine additional UGT1A proteins that act as regulators of glucuronidation activity
Why this work is in the frame
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Bibliographic record
Abstract
BACKGROUND: The gene UGT1 encodes phase II detoxification proteins involved in the elimination of small hydrophobic substances of both endogenous and exogenous origin. To date, nine functional UGT1A proteins are known to be produced from a single gene composed of alternative first exons shared with four common exons. Recently, a novel exon (referred to as exon 5b) was identified in the common shared region. RESULTS: We now reveal a novel alternative splicing mechanism and demonstrate that the exon 5a and the new exon 5b are alternatively spliced, generating several variant mRNAs and up to nine previously unknown variant UGT1A proteins, referred to as isoforms 2 or i2. Isoform-specific RT-PCR analyses reveal that the alternatively spliced mRNAs are widely distributed in human tissues. Immunoreactive proteins at the predicted molecular weight of approximately 45 kDa were confirmed in microsomes of human tissues using antibodies against UGT1A1 and anti-UGT1A7/8/9/10. Functional enzyme assays demonstrate that i2 proteins containing exon 5b are enzymatically inactive. On the other hand, co-expression experiments of i2 of UGT1A1, UGT1A7, UGT1A8 and UGT1A9 with their classical isoform 1 homologs results in a significant repression (15 to 79%) of UGT1A_i1-mediated drug metabolism. CONCLUSION: The UGT1A isoforms 2 act as negative modulators of their isoform 1 homologs in microsome preparations, revealing a new regulatory mechanism of the glucuronidation pathway. Findings further provide the first direct evidence of a novel alternative splicing mechanism at the 3' end of the UGT1 locus that further increases the number of proteins derived from this single gene.
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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 | 0.001 | 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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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 it