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APEX1 / DNA repair nuclease/redox regulator APEX1 · IHC design guide
Design Immunohistochemistry for APEX1
Plan chromogenic paraffin IHC around the ubiquitous nuclear APEX1 staining observed in tissue (HPA tissue IHC). This guide covers fixation, retrieval, antibody titration, controls, and interpretation of possible cytoplasmic signal during regulated nuclear export (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
APEX1 Immunohistochemistry Experimental Design Guide
Expected localisation, validated protocols, controls and antibodies — the at-a-glance facts below, then the full design guide.
Must know before staining
| Expected localisation | Ubiquitous nuclear tissue staining (HPA tissue IHC) | |
| Staining pattern | Nuclear staining across many tissue cell types (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet PA1494) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | None in HPA (detected in all 45 tissues); use no-primary + isotype controls |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections (standard IHC practice; not target-specific); optimize locally. | |
| Caveat | Nitric oxide can promote cytoplasmic APEX1 staining (UniProt) | |
| Regulation | Nucleolar signal varies with cell cycle (UniProt) | |
| Isoform / epitope | No annotated isoforms; mitochondrial chain lacks aa 2–31 (UniProt) |
Section 1
Recommended APEX1 IHC & IF Protocols
Compare the catalog antibody’s IHC-P protocol (datasheet PA1494) with four published APEX1 tissue IHC examples (PMC12149194; PMC5234431; PMC6723795; PMC4554949).
| Sample | Paraffin-embedded human colon adenocarcinoma tissue; fixative not specified (datasheet PA1494) |
| Fixation | Image fixative and duration unreported (datasheet PA1494); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat retrieval: EDTA pH 8.0 (datasheet PA1494); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet PA1494) |
| Primary antibody | Rabbit anti-APEX1, 2-5μg/ml (datasheet PA1494) |
| Primary incubation | Overnight at 4 °C (datasheet PA1494) |
| Detection | HRP-conjugated secondary, DAB chromogen (datasheet PA1494) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | APEX1-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Ubiquitous nuclear expression. No signal in the no-primary control. |
💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet PA1494); test the published Tris–HCl method separately for mouse testes (PMC4554949).
Section 2
What Is the Expected APEX1 Staining Pattern?
APEX1 should show widespread nuclear staining in paraffin tissue sections: HPA reports ubiquitous nuclear expression with Supported reliability and high consistency between antibody staining and RNA data (HPA tissue IHC). Expect stronger staining in the listed High cell populations, including adrenal glandular cells and colon endocrine cells (HPA: High). APEX1 has no transmembrane segment; UniProt also lists nucleolar, cytoplasmic, endoplasmic reticulum and mitochondrial localizations (UniProt P27695 topology and subcellular location).
| Nuclear chromogen appears across multiple cell types, with strong signal in an HPA High population. | This fits the reported ubiquitous nuclear profile and provides a useful positive reference (HPA tissue IHC: Supported; HPA: High). Compare nuclei with the counterstain so pigment or tissue deposits are not mistaken for staining (general IHC practice). |
| Strong, widespread cytoplasmic staining dominates while nuclei remain unstained. | That pattern conflicts with the expected tissue IHC profile (HPA tissue IHC: ubiquitous nuclear expression). Cytoplasmic APEX1 can occur under specific conditions, including nitric oxide stimulated nuclear export, so inspect a positive control and detection controls before calling it artefact (UniProt P27695 subcellular location; general IHC practice). |
| The strongest signal is confined to cardiomyocytes or smooth muscle cells, while an HPA High population is negative. | HPA lists cardiomyocytes and smooth muscle cells as Low, so this distribution warrants a specificity check; Low does not mean absent (HPA tissue IHC: Low). Cross-reactivity or endogenous detection activity is possible; compare no-primary and positive tissue controls (general IHC practice). |
| Chromogen is diffuse across cells, stroma or slide areas without a clear nuclear pattern. | This does not support a compartment-specific APEX1 call (HPA tissue IHC: ubiquitous nuclear expression). Check the no-primary control, blocking and detection steps for nonspecific or endogenous signal before changing the biological interpretation (general IHC practice). |
| An HPA High cell population shows no convincing nuclear signal. | Treat the result as an assay failure to investigate, not evidence that APEX1 is absent: HPA reports High staining in specified populations, including endometrial glandular cells (HPA: High). Review the tissue control, antibody conditions, retrieval and detection using the applicable IHC protocol (general IHC practice). |
💡Expected APEX1 appearanceCall a convincing positive result when nuclei are clearly stained in the relevant cells, especially an HPA High population such as adrenal glandular cells (HPA: High), against a clean background; isolated diffuse deposits or dominant nonnuclear staining without nuclear signal require control review (HPA tissue IHC: ubiquitous nuclear expression; general IHC practice).
| Tissue and cell choice | HPA reports Low tissue specificity at the RNA level and ubiquitous nuclear protein staining; its named High and Low cell populations are relative references, not guaranteed positive and negative controls (HPA tissue IHC). |
| Compartment and cell state | Nuclear staining is the tissue IHC expectation (HPA tissue IHC). UniProt also describes nucleolar localization dependent on cell cycle and active rRNA transcription, plus stimulus linked nuclear to cytoplasmic shuttling; do not require either feature in every section (UniProt P27695 subcellular location). |
| Antibody validation | HPA lists IHC as Supported for HPA002564, CAB004294 and CAB047307; HPA000956 has no listed IHC status (HPA antibodies). Validation status supports selecting an IHC reagent, but the section and controls still determine whether a particular stain is interpretable (general IHC practice). |
| Topology and processing | APEX1 has no transmembrane segment or signal sequence, and UniProt lists protein chains beginning at residues 2 and 32 (UniProt P27695 topology and processing). These annotations do not establish an extracellular staining pattern or predict whether a particular antibody recognizes both chains. |
| IF/ICC Q&A: where should signal appear? | Mainly in the nucleoplasm, with an additional centrosome location (HPA subcellular ICC-IF: nucleoplasm Supported; centrosome Approved). This is an IF/ICC observation, not a paraffin IHC requirement; the IF/ICC guide covers its own workflow. |
| Situation | Likely cause | Next action |
|---|---|---|
| The expected nuclear signal is absent in an HPA High cell population. | The section or assay may have failed; HPA High describes an observed cell population, not a guarantee for every specimen (HPA tissue IHC). | Confirm that the cells are present, examine a known-positive section, then review the catalog antibody's IHC-P conditions, retrieval and detection (general IHC practice). |
| Staining is predominantly cytoplasmic and nuclear staining is weak or absent. | This departs from the usual tissue profile, although UniProt documents regulated nuclear-cytoplasmic shuttling (HPA tissue IHC; UniProt P27695 subcellular location). | Check a positive tissue and no-primary control, and assess whether the pattern is cell-specific and reproducible before assigning biological meaning (general IHC practice). |
| Only HPA Low cells stain strongly. | Cell distribution differs from the HPA reference; cross-reactivity or endogenous detection activity may contribute (HPA tissue IHC: Low; general IHC practice). | Compare an HPA High cell population in parallel and inspect no-primary and detection controls; Low is a relative category, not a required blank (HPA tissue IHC; general IHC practice). |
| Background obscures nuclear boundaries. | Nonspecific antibody binding or detection-system background can prevent compartment scoring (general IHC practice). | Inspect no-primary controls, blocking, antibody dilution and wash steps; score APEX1 only where nuclei can be distinguished from background (general IHC practice; HPA tissue IHC: nuclear profile). |
| Signal appears as coarse deposits rather than cellular staining. | Chromogen precipitate or endogenous detection activity may mimic a positive stain (general IHC practice). | Use the counterstain and no-primary control to distinguish deposits from nuclear signal, then review the detection reagents and staining steps (general IHC practice). |
| A paraffin section lacks the centrosome pattern described for IF/ICC. | The additional centrosome location comes from ICC-IF, while the tissue IHC profile is nuclear (HPA subcellular ICC-IF; HPA tissue IHC). | Judge the paraffin result by nuclear staining in appropriate cells; use the separate IF/ICC guide when assessing subcellular IF images (HPA tissue IHC; HPA subcellular ICC-IF). |
Experiment evidence
IHC & IF images showing APEX1 staining
PA1494 · IHCIHC analysis of APEX1 using anti-APEX1 antibody (PA1494). APEX1 was detected in a paraffin-embedded section of human colon adenocarcinoma ti
PA1494 · IHCIHC analysis of APEX1 using anti-APEX1 antibody (PA1494). APEX1 was detected in a paraffin-embedded section of human spleen tissue. Heat med
PA1494 · IFIF analysis of APEX1 using anti-APEX1 antibody (PA1494). APEX1 was detected in an immunocytochemical section of U2OS cells. Enzyme antigen r
M00627-3 · IHCIHC analysis of APEX1 using anti-APEX1 antibody (M00627-3) . APEX1 was detected in a paraffin-embedded section of human colon cancer tissue.
M00627-3 · IHCIHC analysis of APEX1 using anti-APEX1 antibody (M00627-3) . APEX1 was detected in a paraffin-embedded section of human tonsil tissue. Heat
PB9128 · IHCIHC analysis of APEX1 using anti-APEX1 antibody (PB9128). APEX1 was detected in paraffin-embedded section of human lung cancer tissue. Heat
PB9128 · IHCIHC analysis of APEX1 using anti-APEX1 antibody (PB9128). APEX1 was detected in paraffin-embedded section of mouse brain tissue. Heat mediat
PB9128 · IFIF analysis of APEX1 using anti-APEX1 antibody (PB9128). APEX1 was detected in immunocytochemical section of U20S cell. Enzyme antigen retri
M00627 · IHCIHC analysis of APE1 using anti-APE1 antibody (M00627). APE1 was detected in paraffin-embedded section of human intestinal cancer tissue. He
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000100823-APEX1/tissue/cerebral+cortex#imid_904312
HPA · EsophagusHuman Protein Atlas IHC, Esophagus. Source: https://www.proteinatlas.org/ENSG00000100823-APEX1/tissue/esophagus#imid_904276
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000100823-APEX1/tissue/colon#imid_904222
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000100823-APEX1/tissue/liver#imid_904239
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA002564; green = APEX1, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA002564; green = APEX1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for APEX1 IHC & IF
🧪Run colon first and score its endocrine cells, which have High APEX1 staining (HPA: colon endocrine cells, High). HPA detects APEX1 in all 45 scored tissues, so use no-primary and isotype controls in place of a negative tissue; cells without specific signal on the positive slide should show counterstain alone, but no colon cell type is established as an internal biological negative (HPA: no negative tissue rows).
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: None in HPA: APEX1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead.
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show APEX1 in A-431, U-251MG, U2OS, with annotated localisation: Nucleoplasm (supported) (HPA subcellular).
Technical controls: Include a no-primary, secondary-only control; a rabbit IgG control matched to the primary antibody’s clonality where applicable; and APEX1-knockout material as a biological specificity control (caption: rabbit anti-APEX1 primary; standard IHC practice). Quench endogenous peroxidase and check for background DAB signal in the colon section (caption: HRP/DAB detection; standard IHC practice).
⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected PA1494 paraffin-section caption does not state the fixative (caption: PA1494). That caption uses heat retrieval in EDTA at pH 8.0, so begin with that condition, but it does not establish that retrieval is required for every specimen (caption: PA1494). The supplied evidence does not establish whether frozen sections or IF are easier; for IF, nucleoplasmic signal is supported, and colon autofluorescence should be checked with an unstained section (HPA: subcellular location; standard IF practice).
HPA tissue IHC evidence for APEX1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — High consistency between antibody staining and RNA expression data.). Rows are taken directly from the HPA tissue chart — click any row's HPA link to view the source.
Positive expression · recommended positive controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adrenal gland | Glandular cells | High | Protein (IHC) | HPA → |
| Appendix | Endocrine cells | High | Protein (IHC) | HPA → |
| Breast | Adipocytes | High | Protein (IHC) | HPA → |
| Cerebellum | GLUC cells - nucleus | High | Protein (IHC) | HPA → |
| Colon | Endocrine cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: APEX1 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced APEX1 IHC Tips
Use the documented PA1494 paraffin-section conditions as the IHC starting point, then evaluate nuclear staining, compartment shifts, and tissue background against matched controls.
How should I troubleshoot weak APEX1 staining after antigen retrieval?
Start with heat-mediated retrieval in EDTA at pH 8.0 for paraffin sections (datasheet PA1494). If staining is weak, verify that sections reached the intended retrieval temperature and compare a short and longer heating interval on adjacent sections while keeping the buffer fixed (standard IHC practice). The documented image used 2 μg/ml primary antibody overnight at 4°C, so match those conditions before attributing weak signal to retrieval (datasheet PA1494). Judge improvement by nuclear staining across viable cells, while watching for tissue damage or rising background from harsher heating (HPA: ubiquitous nuclear expression; standard IHC practice).
Could fixation explain weak or uneven APEX1 staining in paraffin sections?
The PA1494 paraffin-section caption does not state a fixative, so APEX1-specific fixation sensitivity is unknown (datasheet PA1494). Record the specimen's actual fixative and duration, then compare sections processed with matched retrieval and detection conditions before assigning a fixation effect (standard IHC practice). Check whether weak signal tracks thick sections, folds, or uneven reagent access, and inspect a well-preserved internal nuclear reference on each slide (standard IHC practice; HPA: ubiquitous nuclear expression). Keep the documented EDTA retrieval at pH 8.0 and 2 μg/ml overnight primary incubation constant during that comparison (datasheet PA1494).
How should I assess cytoplasmic or punctate APEX1 staining?
Score nucleoplasmic staining first because tissue IHC shows ubiquitous nuclear expression and cell imaging supports nucleoplasm as the main location (HPA tissue IHC; HPA subcellular). APEX1 is also reported in nucleoli, nuclear speckles, cytoplasm, endoplasmic reticulum, and mitochondria, so a reproducible secondary pattern deserves examination rather than automatic rejection (UniProt P27695 subcellular location). Its nucleolar localisation depends on cell cycle and active rRNA transcription, while nitric oxide can promote nuclear-to-cytoplasmic movement (UniProt P27695 subcellular location). Compare the suspected compartment in adjacent viable cells and replicate sections, recording nuclear and cytoplasmic scores separately (standard IHC practice).
Could APEX1 processing or modification alter antibody recognition in tissue?
The record lists no annotated isoforms, but describes chains spanning residues 2–318 and 32–318, the latter designated mitochondrial (UniProt P27695 processing; UniProt P27695 isoforms). An antibody recognizing the extreme N terminus could therefore detect those chains differently; the PA1494 caption does not identify its epitope (UniProt P27695 processing; datasheet PA1494). N-terminal acetylation is reported at residues 6, 7, 27, 31, and 32, making epitope accessibility a question to test rather than an established staining effect (UniProt P27695 modified residues). Check the antibody's documented immunogen or epitope and compare compartment patterns with an independently mapped antibody if available (standard IHC validation practice).
How can IF help evaluate APEX1 localisation alongside cell identity?
For a separate IF experiment, pair APEX1 with a marker for the cell population under study and a nuclear counterstain, then inspect signal within identified cells (standard IF practice). Select spectrally separated fluorophores and place the weaker signal in a channel with low measured tissue autofluorescence; include unstained and single-stain controls when multiplexing (standard IF practice). APEX1 has no transmembrane segment and is mainly nucleoplasmic, so nuclear epitopes generally require permeabilisation, although the PA1494 epitope is unspecified (UniProt P27695 topology; HPA subcellular; datasheet PA1494). Optimise permeabilisation and fixation for that IF assay without treating the PA1494 paraffin IHC caption as IF validation (standard IF practice; datasheet PA1494).
What controls help distinguish APEX1 signal from chromogenic background?
The documented tissue image used 10% goat serum blocking, rabbit PA1494 primary at 2 μg/ml overnight at 4°C, and peroxidase detection with DAB (datasheet PA1494). Include a no-primary control and an endogenous peroxidase block to identify staining produced by the detection system rather than bound primary antibody (standard chromogenic IHC practice). If diffuse brown signal persists, compare primary titrations, wash quality, and DAB development under otherwise matched conditions (standard IHC practice). Evaluate viable nuclei as the principal expected compartment, and do not call low-staining heart or smooth muscle cells truly negative controls (HPA tissue IHC: ubiquitous nuclear expression; HPA tissue IHC: low staining in cardiomyocytes and smooth muscle cells).
How should I quantify APEX1 staining across paraffin tissue sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define viable regions and cell populations before scoring, because APEX1 tissue staining is broadly nuclear and cell composition can differ across fields (HPA tissue IHC; standard IHC scoring practice). Record nuclear percent-positive cells and intensity, or calculate an H-score from 0–300 using intensity categories 0–3 (standard IHC scoring practice). Report cytoplasmic staining separately rather than folding it into the nuclear score, given the protein's documented compartment diversity (UniProt P27695 subcellular location). Normalise cell counts to the number of viable cells assessed, or report positive-cell density per mm² of viable tissue; keep thresholds and imaging conditions consistent (standard IHC scoring practice).
When is an unusual APEX1 pattern credible rather than artefactual?
A convincing result shows reproducible staining in viable cells with a predominantly nuclear pattern, consistent with supported tissue IHC and nucleoplasmic cell imaging (HPA tissue IHC; HPA subcellular). Cytoplasmic or nucleolar signal can be plausible, but should persist across comparable sections and be scored separately because APEX1 has documented localisation beyond the nucleoplasm (UniProt P27695 subcellular location; standard IHC practice). Treat staining restricted to tissue edges, folds, or necrotic areas cautiously and compare it with adjacent intact tissue (standard IHC practice). Check no-primary and peroxidase-block controls before interpreting brown deposits, particularly where endogenous enzyme activity could mimic DAB signal (standard chromogenic IHC practice).
Boster reagents
Best APEX1 / DNA repair nuclease/redox regulator APEX1 IHC Antibodies
Catalog antibodies have paraffin-section IHC images from human, mouse and rat tissues (IHC captions: PA1494, M00627-3, PB9128); PA1494 and PB9128 also have cell and tissue IF images (IF captions).
Real IHC data
Anti-APE1/APEX1 Antibody ®
Cat # PA1494
Real IHC data
Anti-APE1 Rabbit Monoclonal Antibody
Cat # M00627-3
Real IHC data
Anti-APE1/APEX1 Antibody ®
Cat # PB9128
Real IHC data
Anti-APE1 APEX1 Antibody ® (monoclonal, 5C11)
Cat # M00627
PA1494 shows IHC in human colon adenocarcinoma, spleen and prostatic cancer and mouse liver; M00627-3 shows IHC in human colon cancer and tonsil, mouse liver and rat liver (IHC captions: PA1494, M00627-3). PB9128 shows IHC in human lung cancer and mouse and rat brain, while M00627 shows IHC in human intestinal cancer (IHC captions: PB9128, M00627).
Which to pick: For paraffin-section IHC across human, mouse and rat, choose rabbit monoclonal M00627-3 if clonality matters; its IHC captions cover all 3 species and describe EDTA retrieval at pH 8.0 (catalog: clone 17A44; IHC captions: M00627-3). For IF/ICC, choose PA1494 for its human cell and human and rat tissue IF images, or PB9128 for its human cell and tissue IF images (IF captions: PA1494, PB9128). PB9128 also has paraffin-section IHC images across human, mouse and rat with citrate retrieval at pH 6; the IHC captions report paraffin embedding but do not report the fixative (IHC captions: PB9128).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry P27695 (APEX1_HUMAN, DNA repair nuclease/redox regulator APEX1).
- Human Protein Atlas. APEX1 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. APEX1 subcellular location (ICC-IF): Mainly localized to the nucleoplasm. In addition localized to the centrosome..
- Human Protein Atlas. APEX1 antibody validation summary (4 antibodies).
- Isoliensinine exerts antitumor effects in lung adenocarcinoma by inhibiting APEX1-driven ROS production. Frontiers in pharmacology 2025 — PMC12149194.
- Clinical implications of APEX1 and Jagged1 as chemoresistance factors in biliary tract cancer. Annals of surgical treatment and research 2017 — PMC5234431.
- APEX1 Expression as a Potential Diagnostic Biomarker of Clear Cell Renal Cell Carcinoma and Hepatobiliary Carcinomas. Journal of clinical medicine 2019 — PMC6723795.
- Increased human AP endonuclease 1 level confers protection against the paternal age effect in mice. Mutation research 2015 — PMC4554949.
- PubMed PMID:1719477 — UniProt-cited evidence.
- PubMed PMID:1722334 — UniProt-cited evidence.
- PubMed PMID:1627644 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for APEX1 (DNA repair nuclease/redox regulator APEX1). Expected localisation Ubiquitous nuclear tissue staining (HPA tissue IHC). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet PA1494). Validated IHC antibody: PA1494 at 2-5μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative None in HPA (detected in all 45 tissues); use no-primary + isotype controls. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human colon adenocarcinoma tissue; fixative not specified (datasheet PA1494); 2. Fixation: Image fixative and duration unreported (datasheet PA1494); verify before use.; 3. Sectioning: 4–5 µm sections on charged slides (standard); 4. Deparaffinisation: Xylene, graded ethanol series to water (standard); 5. Antigen retrieval: Heat retrieval: EDTA pH 8.0 (datasheet PA1494); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet PA1494); 8. Primary antibody: Rabbit anti-APEX1, 2-5μg/ml (datasheet PA1494); 9. Primary incubation: Overnight at 4 °C (datasheet PA1494). Watch for: Fixation: Keep fixation consistent across sections (standard IHC practice; not target-specific); optimize locally.; Caveat: Nitric oxide can promote cytoplasmic APEX1 staining (UniProt); Isoform / epitope: No annotated isoforms; mitochondrial chain lacks aa 2–31 (UniProt); Regulation: Nucleolar signal varies with cell cycle (UniProt). Evidence: UniProt P27695, HPA tissue IHC · Supported, HPA ICC-IF · Mainly localized to the nucleoplasm. In addition localized to the…, Datasheet PA1494, PMC12149194, PMC5234431. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/APEX1/immunohistochemistry-ihc-guide.