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P3R3URF is described in available literature only as a putative upstream-ORF/readthrough-associated product distinct from canonical PIK3R3.
"P3R3URF is described in the available tool-retrieved literature as an upstream open reading frame (uORF)/readthrough-associated entity located upstream of the canonical human gene PIK3R3. However, direct, P3R3URF-specific functional evidence is very limited in the accessible corpus."
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In the Tidball 2023 CRISPRi study in human iNeurons, qRT-PCR detected canonical PIK3R3 but not P3R3URF or P3R3URF-PIK3R3 transcripts; the authors favored a post-translational modification of PIK3R3 over a P3R3URF readthrough.
"Direct transcript testing found detectable PIK3R3, but no detectable P3R3URF-PIK3R3 or P3R3URF transcripts ... Authors' conclusion for the higher-MW band: possibly a post-translational modification rather than the readthrough product."
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Pathway conclusions from the Tidball study apply to canonical PIK3R3, not P3R3URF.
"Functional signaling data in the study support a role for PIK3R3 (p55gamma), not specifically P3R3URF, in upstream PI3K/AKT/mTOR signaling ... 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."
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A substantial fraction of upstream/noncanonical ORFs do not yield stable peptides, providing context for the lack of detection of P3R3URF.
">80% of noncanonical peptides have low PepScores (<0.3), consistent with widespread translation that often yields unstable/undetectable products."