Component
UGA recoding
Context-dependent decoding of UGA as selenocysteine during selenoprotein translation.
4 recorded relationships. Experimental role, claim status and evidence remain attached to each record.
How nutrients influence it
Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.
Other things that act on it
Enzymes, hormones, genes, and other components with a recorded effect. These are not nutrients, so they do not count toward the arrows above. Each finding names the chapter that recorded it.
How nutrients reach it in more than one step
Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.
Tracing routes…
What it does
Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.
What acts on it
Experimental FTSJ1 loss reduces efficient selenocysteine insertion at UGA.
Experimental context and source evidence
- availability_state
- Experimental loss of FTSJ1-dependent tRNA modification.
- experimental_scope
- Cell/biochemical studies and melanoma xenograft models reported in the 2024 FTSJ1 study.
- limitations
- FTSJ1 loss is a machinery perturbation, not itself a nutritional selenium-deficiency syndrome. The results do not prove that Um34 determines every selenoprotein phenotype.
- trigger_kind
- machinery_impairment
Selenium deficiency: a mechanism-first reference · lines 75–75
Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft
Update: FTSJ1 was identified in 2024 as the tRNA^[Ser]Sec Um34 methyltransferase. Loss of FTSJ1 reduced efficient Sec insertion and sensitized experimental cells to oxidative stress. Evidence: cell/biochemical and melanoma xenograft models. [1]
Complete structured claim and evidenceA constrained Sec-tRNA supply can impair selenocysteine insertion at UGA in a transcript-dependent manner.
Experimental context and source evidence
- availability_state
- Selenium intake or availability becomes inadequate for the cellular context.
- experimental_scope
- Biochemical pathway and experimental shortage model; effects depend on transcript and tissue.
- limitations
- This is a conditional supply constraint, not a prediction that all selenoproteins fall equally. No validated plasma cutoff is assigned.
- trigger_kind
- nutrient_deficiency
Selenium deficiency: a mechanism-first reference · lines 35–45
Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft
Sec-tRNA^[Ser]Sec ↓ eEFSec ribosome reaches UGA ↓ SECIS + SECISBP2/SBP2 machinery ↓ SELENOCYSTEINE INSERTED SerRS charging tRNA^[Ser]Sec with serine is an obligatory biosynthetic step, not a mistake. SEPHS2 supplies selenophosphate, while PSTK and SEPSECS convert the serine-charged tRNA into Sec-tRNA^[Ser]Sec. UGA recoding is intrinsically less straightforward than ordinary amino-acid insertion and its efficiency varies substantially by transcript and cellular context. It should not be treated as a universal 5–10% process across all selenoprotein mRNAs.
Selenium deficiency: a mechanism-first reference · lines 783–790
Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft
selenium intake / availability ↓ │ ▼ central selenium metabolism and Sec-tRNA supply become constrained │ ├─ tRNA^[Ser]Sec modification can shift (including Um34 / FTSJ1 biology) ├─ SECIS-dependent UGA recoding changes ├─ selected transcripts can undergo stronger repression / NMD
Complete structured claim and evidenceSECISBP2 deficiency compromises a required component of SECIS-dependent selenocysteine decoding.
Experimental context and source evidence
- availability_state
- Rare genetic SECISBP2 deficiency, distinct from inadequate dietary selenium.
- experimental_scope
- Rare human genetic disorder and biochemical role of SECIS-dependent recoding.
- limitations
- Growth, muscle, and reproductive findings in genetic disease are not direct phenocopies of ordinary dietary deficiency. Adequate intake does not define machinery function.
- trigger_kind
- machinery_impairment
Selenium deficiency: a mechanism-first reference · lines 35–41
Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft
Sec-tRNA^[Ser]Sec ↓ eEFSec ribosome reaches UGA ↓ SECIS + SECISBP2/SBP2 machinery ↓ SELENOCYSTEINE INSERTED
Selenium deficiency: a mechanism-first reference · lines 83–83
Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft
Layer 2 — SECIS-dependent translation. SECIS structure, SECISBP2/SBP2 interactions, eEFSec, ribosomal context, and other RNA-binding proteins influence recoding efficiency.
Selenium deficiency: a mechanism-first reference · lines 497–509
Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft
Rare genetic disorders help show what happens when parts of selenoprotein biology fail despite adequate dietary selenium. Gene / protein Disorder or molecular role Selected phenotype / implication SECISBP2 (SBP2) SECISBP2 deficiency Abnormal thyroid-hormone profile, growth and muscle phenotypes, male infertility and other multisystem effects
Complete structured claim and evidenceHuman SECIS elements show widely differing reporter recoding activities, precluding a universal endogenous 5–10 percent efficiency inference.
Experimental context and source evidence
- cell_type
- HEK293 and HepG2 reporters
- experimental_model
- 26 human SECIS reporters in HEK293/HepG2 and cell-free translation
- limitations
- Reporter activity is not a direct count of all endogenous translation outcomes.
- organism
- Homo sapiens
Selenium: literature corrections and mechanism additions · lines 1203–1213
Metabolic Ledger literature curation, 17 September 2026; primary papers linked individually · supports · 26 human SECIS reporters in HEK293/HepG2 and cell-free translation · secondary_verified · secondary_verified
## secis-variable Efficiency depends on the RNA and test conditions. Human SECIS elements show widely differing reporter recoding activities, precluding a universal endogenous 5–10 percent efficiency inference. Organism: Homo sapiens Cell type: HEK293 and HepG2 reporters Experimental model: 26 human SECIS reporters in HEK293/HepG2 and cell-free translation Limitations: Reporter activity is not a direct count of all endogenous translation outcomes. Primary reference: [Novel structural determinants in human SECIS elements modulate the translational recoding of UGA as selenocysteine](https://pmc.ncbi.nlm.nih.gov/articles/PMC2761289/)
Complete structured claim and evidence
The events it takes part in
A mechanism often involves more than two components. These are the full events, with every participant and its role.
Situations it appears in
Low-supply and faulty-machinery situations recorded in the chapters where this component plays a part.
In the sources
Preserved passages that mention this component, quoted exactly. Open one to read it in context.
Open hypotheses
Proposed ideas that involve this component. They are labeled as hypotheses and do not change any recorded statement.
This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.