| Claim/Observation | Evidence type | Quantitative result | Interpretation/limitations | Source (with DOI/URL and year) |
|---|---|---|---|---|
| Target identity check: **P3R3URF** is discussed in the available literature only as a putative product related to an **open reading frame upstream of PIK3R3**; it is **not the same entity as canonical PIK3R3/p55γ** | Identity verification from article text | No direct abundance value reported | Available experimental paper centers on **PIK3R3** knockdown in human iNeurons and mentions P3R3URF only to test whether a higher-MW band might represent a readthrough/fusion product; this helps avoid conflating the poorly characterized uORF product with the well-studied PI3K regulatory subunit PIK3R3 | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |
| P3R3URF is described as a **“known fusion readthrough protein”** arising from an upstream ORF relative to **PIK3R3** | Literature description / inference cited by authors | None reported | This is a descriptive statement in the paper, not a direct demonstration in that study; the authors explicitly tested this possibility experimentally | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |
| Canonical **PIK3R3** protein is robustly reduced by on-target CRISPRi in human iNeurons | Immunoblot | **83% reduction** in PIK3R3 protein | Strong evidence that the gRNA effectively knocks down canonical PIK3R3; this measurement does **not** by itself establish expression of P3R3URF | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |
| Canonical **PIK3R3 mRNA** is reduced by the on-target gRNA | qRT-PCR | **70% reduction** in PIK3R3 mRNA | Confirms transcript-level knockdown of canonical PIK3R3; again, this does not prove translation of P3R3URF | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |
| A **second, higher-molecular-weight band** was observed on the PIK3R3 immunoblot and was also reduced by the PIK3R3-targeting gRNA | Immunoblot / figure inspection | Band reduced by the **same approximate amount** as canonical PIK3R3 (no exact % given) | The band size was considered compatible with a possible P3R3URF-related readthrough product, but the result is not definitive; altered mobility could also reflect post-translational modification of PIK3R3 | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001, pqac-00000004) |
| Direct transcript testing found **detectable PIK3R3**, but **no detectable P3R3URF-PIK3R3 or P3R3URF transcripts** | qRT-PCR | Detectable transcript: **PIK3R3 only**; undetected: **P3R3URF-PIK3R3** and **P3R3URF** | This is the key experimental point arguing **against** the higher-MW band being a readily detectable P3R3URF readthrough transcript in this system; negative qRT-PCR does not fully exclude extremely low abundance, condition-specific, or technically missed transcripts | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |
| Authors’ conclusion for the higher-MW band: **possibly a post-translational modification** rather than the readthrough product | Interpretation of combined immunoblot + qRT-PCR | None reported | This is the study’s favored interpretation in their human iNeuron system; it remains provisional because the band was not identified by orthogonal proteomics or sequencing | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |
| Functional signaling data in the study support a role for **PIK3R3 (p55γ)**, not specifically P3R3URF, in upstream PI3K/AKT/mTOR signaling | CRISPRi functional assays (immunoblot for phospho-signaling) | PIK3R3 knockdown increased AKT phosphorylation; authors state only **PIK3R3 and HIP1** affected the upstream PI3K/mTOR/S6 pathway | These pathway conclusions should be attributed to **canonical PIK3R3** because the same study did not detect P3R3URF-related transcripts; functional extrapolation to P3R3URF would be unsupported | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001, pqac-00000002, pqac-00000003) |
| Current experimental support for human **P3R3URF (UniProt A0A087WWA1; HGNC:53451)** is therefore **limited/ambiguous** in the available source | Evidence synthesis | One study mentions and tests for it; no positive transcript detection in that system | Best-supported statement is that P3R3URF is a **putative upstream-ORF/readthrough-associated product** distinguished from canonical PIK3R3; direct evidence for its independent expression, localization, or function in human cells remains lacking in the cited source | Tidball et al., bioRxiv, 2023, DOI: 10.1101/2023.12.13.571474, https://doi.org/10.1101/2023.12.13.571474 (pqac-00000000, pqac-00000001) |


*Table: This table summarizes what the available cited evidence does and does not support for human P3R3URF, clearly separating the putative upstream-ORF/readthrough annotation from experimentally demonstrated effects on canonical PIK3R3. It is useful for identity verification and for avoiding conflation with the PI3K regulatory subunit p55γ.*