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CPSF6 / Cleavage and polyadenylation specificity factor subunit 6 · IHC design guide
Design Immunohistochemistry for CPSF6
Plan CPSF6 chromogenic IHC around the ubiquitous nuclear staining observed in tissues (HPA tissue IHC). This guide covers consistent fixation, antibody titration at 2–5 μg/ml (datasheet A04551-1), and interpretation of possible nuclear–cytoplasmic shuttling (UniProt).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
CPSF6 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 | Nuclear staining observed; cytoplasmic shuttling reported (HPA tissue IHC; UniProt) | |
| Staining pattern | Ubiquitous nuclear staining across tissue cells (HPA tissue IHC) | |
| Antigen retrieval | EDTA pH 8.0 HIER, heat-mediated (datasheet A04551-1) | |
| Positive control | Adipose tissue+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 | Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A04551-1) | |
| Caveat | Nuclear–cytoplasmic shuttling may alter the pattern (UniProt) | |
| Regulation | No expression regulator annotated (UniProt) | |
| Isoform / epitope | 3 isoforms; verify antibody epitope coverage (UniProt) |
Section 1
Recommended CPSF6 IHC & IF Protocols
The catalog antibody uses heat-mediated EDTA pH 8.0 retrieval (datasheet A04551-1). Published IHC protocols cover HCC and breast cancer tissue microarrays (PMC11234225; PMC5514498).
| Sample | Paraffin-embedded human liver cancer tissue; fixative not specified (datasheet A04551-1) |
| Fixation | Image fixative and duration unreported (datasheet A04551-1); 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 A04551-1); 20 min, 95–100 °C (standard) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% goat serum (datasheet A04551-1) |
| Primary antibody | Rabbit anti-CPSF6, 2-5 μg/ml (datasheet A04551-1) |
| Primary incubation | Overnight at 4 °C (datasheet A04551-1) |
| Detection | Streptavidin-biotin complex (SABC), DAB chromogen (datasheet A04551-1) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | CPSF6-positive staining in adipocytes of adipose tissue (HPA tissue IHC: High). HPA tissue profile: Ubiquitous nuclear expression. No signal in the no-primary control. |
💡Decision noteStart with EDTA pH 8.0 for the catalog antibody (datasheet A04551-1); compare citrate pH 6.0 if retrieval needs optimization (PMC5514498).
Section 2
What Is the Expected CPSF6 Staining Pattern?
CPSF6 should appear predominantly in nuclei, consistent with its nucleoplasmic and nuclear-speckle localization (UniProt Q16630; HPA: nucleoplasm and nuclear speckles). Expect staining across many cell types rather than a restricted tissue compartment (HPA: ubiquitous nuclear expression; low tissue specificity). HPA rates the tissue IHC pattern Supported, with medium consistency between antibody staining and RNA expression (HPA: tissue IHC). CPSF6 has no transmembrane segment (UniProt Q16630: topology).
| Nuclear staining in multiple cell types, with some variation between nuclei. | This fits the broad tissue pattern (HPA: ubiquitous nuclear expression). Compare identifiable cells within the same section: HPA reports High staining in adipocytes, respiratory epithelial cells, glial cells and bone-marrow hematopoietic cells (HPA: tissue IHC). These examples are useful positive references, not a required intensity for every cell. |
| Nuclei show uneven or punctate signal. | Nucleoplasmic and speckle-associated localization makes nuclear texture plausible (HPA: enhanced nucleoplasm and nuclear speckles in ICC-IF). UniProt also describes paraspeckle-associated puncta whose distribution varies with the cell cycle (UniProt Q16630: subcellular location). Chromogenic IHC may not resolve these structures; judge the overall nuclear compartment first. |
| Strong staining is mainly cytoplasmic or outlines cell membranes. | Predominantly cytoplasmic staining conflicts with the observed tissue IHC pattern (HPA: ubiquitous nuclear expression). CPSF6 can shuttle between nucleus and cytoplasm (UniProt Q16630: subcellular location), so isolated cytoplasmic signal is not automatically false; membrane outlining is unexpected for a protein without a transmembrane segment (UniProt Q16630: topology). |
| An isolated cell population stains while surrounding expected-positive nuclei do not. | Treat the apparent cell restriction cautiously: HPA describes ubiquitous nuclear expression and low tissue specificity (HPA: tissue IHC). Check morphology and controls for cross-reactivity or endogenous detection activity (general IHC practice). Do not label that population CPSF6-positive solely because it contains chromogen. |
| Diffuse color covers nuclei, cytoplasm and empty areas, or no nuclei stain in a positive-reference section. | Diffuse, compartment-independent color limits localization calls (general IHC practice). An absent signal in a section containing a documented High-staining cell population conflicts with the HPA reference pattern (HPA: tissue IHC); inspect controls and processing before interpreting it as biological loss. |
💡Expected CPSF6 appearanceCall a section positive when identifiable cells show chiefly nuclear signal, ideally clear above local background; HPA reports High staining in several tissue cell populations (HPA: tissue IHC). Predominant membrane outlining or uniform color outside cells is suspect (UniProt Q16630: topology; general IHC practice).
| Tissue reference and confidence | HPA reports ubiquitous nuclear expression and Low tissue specificity, with Supported IHC reliability and medium staining–RNA consistency (HPA: tissue IHC). Use its High-staining examples as references, while allowing biological and assay variation. |
| Subnuclear distribution | Nucleoplasm and nuclear speckles are enhanced in ICC-IF images (HPA: subcellular). UniProt also places CPSF6 in paraspeckle-associated puncta and notes cell-cycle variation (UniProt Q16630: subcellular location); these details may exceed chromogenic IHC resolution. |
| Isoforms and antibody recognition | UniProt lists three CPSF6 isoforms (UniProt Q16630: isoforms). The supplied sources do not map this section's IHC antibody epitope to an isoform; avoid interpreting cell-to-cell intensity differences as isoform changes without separate evidence. |
| Processing and membrane pattern | The annotated chain spans residues 1–551, with no signal peptide or propeptide and no transmembrane segment (UniProt Q16630: processing and topology). Those annotations offer no basis for expecting a shed extracellular or membrane-rim IHC pattern. |
| IF/ICC: what should I expect? | Expect nucleoplasmic signal and nuclear speckles (HPA: subcellular ICC-IF); HPA039973 has Enhanced ICC validation but Supported IHC validation (HPA: antibodies). IF/ICC staining conditions belong to its separate guide; ICC validation does not specify this section's IHC conditions. |
| Situation | Likely cause | Next action |
|---|---|---|
| Nuclear staining is weak throughout a section that contains an HPA High-staining cell population. | The result falls short of the reference pattern (HPA: tissue IHC); antibody performance or a general staining-step failure is possible (general IHC practice). | Check the positive-control section and reagent sequence; optimize retrieval and primary-antibody dilution using the antibody's IHC-P instructions (general IHC practice). No CPSF6-specific retrieval setting or dilution is supplied. |
| Chromogen appears broadly in cytoplasm or extracellular space. | The pattern obscures the reported nuclear distribution (HPA: tissue IHC) and may reflect nonspecific staining or detection background (general IHC practice). | Compare with a no-primary control; review blocking, washes and detection chemistry, then reassess nuclear signal against local background (general IHC practice). |
| A few isolated cells stain strongly while nearby nuclei appear blank. | A sharply restricted pattern conflicts with low tissue specificity and ubiquitous nuclear expression (HPA: tissue IHC); cross-reactivity or endogenous detection activity remains possible (general IHC practice). | Identify the stained cells by morphology, inspect a no-primary control, and compare with a documented High-staining reference cell population (HPA: tissue IHC; general IHC practice). |
| Only membrane rims stain. | A membrane-rim pattern is inconsistent with the lack of a transmembrane segment and the predominantly nuclear reference pattern (UniProt Q16630: topology; HPA: tissue IHC). | Review controls and antibody specificity before scoring; record nuclear and membrane signal separately (general IHC practice). Do not count rim-only staining as the expected CPSF6 result. |
| Nuclear staining is visible but appears smooth rather than punctate. | Chromogenic sections may not resolve nuclear speckles that are enhanced in ICC-IF images (HPA: subcellular); puncta also vary with the cell cycle (UniProt Q16630: subcellular location). | Assess whether signal is chiefly nuclear and above background (HPA: tissue IHC; general IHC practice). Reserve fine subnuclear-pattern questions for the separate IF/ICC guide. |
| The test section is negative and the positive-control section is also negative. | A shared assay problem is more plausible than a tissue-specific CPSF6 absence when the reference is HPA's ubiquitous nuclear pattern (HPA: tissue IHC; general IHC practice). | Check tissue integrity, reagent sequence, retrieval and detection controls before interpreting the test section; use the antibody's IHC-P instructions for assay settings (general IHC practice). |
Experiment evidence
IHC & IF images showing CPSF6 staining
A04551-1 · IHCIHC analysis of CPSF6 using anti-CPSF6 antibody (A04551-1). CPSF6 was detected in a paraffin-embedded section of human liver cancer tissue.
A04551-1 · IHCIHC analysis of CPSF6 using anti-CPSF6 antibody (A04551-1). CPSF6 was detected in a paraffin-embedded section of human liver cancer tissue.
A04551-1 · IFIF analysis of CPSF6 using anti-CPSF6 antibody (A04551-1). CPSF6 was detected in an immunocytochemical section of MCF-7 cells. Enzyme antige
M04551 · IHCIHC analysis of CPSF6 using anti-CPSF6 antibody (M04551). CPSF6 was detected in a paraffin-embedded section of human squamous cell carcinoma
M04551 · IHCIHC analysis of CPSF6 using anti-CPSF6 antibody (M04551). CPSF6 was detected in a paraffin-embedded section of human cervical cancer tissue.
M04551 · IFIF analysis of CPSF6 using anti-CPSF6 antibody (M04551). CPSF6 was detected in an immunocytochemical section of U20S cells. Enzyme antigen r
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000111605-CPSF6/tissue/cerebral+cortex#imid_10365913
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000111605-CPSF6/tissue/colon#imid_10365839
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000111605-CPSF6/tissue/liver#imid_10365832
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000111605-CPSF6/tissue/kidney#imid_10365833
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA039973; green = CPSF6, blue = nucleus, red = microtubules.
HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody HPA039973; green = CPSF6, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for CPSF6 IHC & IF
🧪Run bone marrow first and assess CPSF6 staining in hematopoietic cells (HPA: High in bone marrow hematopoietic cells). HPA detects CPSF6 in all 45 scored tissues, so there is no documented negative tissue; use no-primary and isotype controls, and regard any intact counterstained cells without nuclear DAB signal as provisional internal negatives rather than a validated negative cell type (HPA: no negative rows; standard IHC practice).
Positive control tissue: Adipose tissue (Adipocytes, HPA High)
Negative control tissue: None in HPA: CPSF6 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 CPSF6 in A-431, U-251MG, U2OS, HEK293, U2OS, siRNA 1 (10x), U2OS, siRNA 1 (40x), U2OS, siRNA 2 (10x), U2OS, siRNA 2 (40x), U2OS, scrambled (10x), U2OS, scrambled (40x), with annotated localisation: Nucleoplasm (enhanced), Nuclear speckles (enhanced) (HPA subcellular).
Technical controls: Include a secondary-only section, a concentration-matched rabbit IgG control matched to the primary antibody’s clonality class, and a CPSF6 knockout specimen if available (selected-SKU IHC caption: rabbit primary; standard IHC practice). Quench endogenous peroxidase in bone marrow before DAB detection, since hematopoietic cells can generate peroxidase background (standard IHC practice).
⚠️Feasibility: A CPSF6-specific fixation window or fixation effect is unreported, and the selected A04551-1 paraffin-section caption does not state a fixative (selected-SKU IHC caption: fixative unreported). The caption uses heat-mediated EDTA retrieval at pH 8.0, but it does not establish that retrieval is required; the supplied evidence also does not show that frozen sections or IF are easier (selected-SKU IHC caption: EDTA pH 8.0). In bone marrow, endogenous peroxidase can obscure chromogenic staining unless quenched (standard IHC practice).
HPA tissue IHC evidence for CPSF6
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Supported — Medium 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 |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | High | Protein (IHC) | HPA → |
| Adrenal gland | Glandular cells | High | Protein (IHC) | HPA → |
| Appendix | Glandular cells | High | Protein (IHC) | HPA → |
| Bone marrow | Hematopoietic cells | High | Protein (IHC) | HPA → |
| Breast | Adipocytes | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| None in HPA: CPSF6 is detected in all 45 scored tissues. Use a no-primary (secondary-only) and an isotype control instead. | ||||
Section 3
Advanced CPSF6 IHC Tips
Troubleshoot CPSF6 staining in paraffin sections by checking retrieval, nuclear localisation, assay controls and scoring before interpreting differences between samples.
How should I retrieve CPSF6 in paraffin sections when nuclear staining is weak?
Start with heat-mediated antigen retrieval in EDTA at pH 8.0 for paraffin sections (datasheet A04551-1). The selected image used this retrieval before incubation with 2 μg/ml catalog antibody overnight at 4°C (datasheet A04551-1). If staining is weak, compare retrieval heating and cooling across matched sections while keeping antibody concentration and detection conditions fixed (standard IHC practice). Assess recovery in intact nuclei rather than judging total brown signal, because CPSF6 is principally nucleoplasmic and associated with nuclear speckles (HPA subcellular). Include a section processed without primary antibody to distinguish recovered signal from detection background (standard IHC practice).
Could fixation be masking CPSF6 staining in my tissue sections?
The selected paraffin-section caption does not state a fixative, so target-specific CPSF6 sensitivity to fixation is unknown (datasheet A04551-1). Record each sample’s fixative and fixation duration before comparing staining, since fixation and processing can affect epitope accessibility in paraffin IHC (standard IHC practice). Test matched sections with the stated EDTA retrieval at pH 8.0 and the catalog antibody at 2 μg/ml to limit other sources of variation (datasheet A04551-1). Compare nuclear signal in morphologically intact cells and inspect poorly preserved or damaged areas separately (HPA tissue IHC; standard IHC practice). Do not assign a CPSF6-specific fixation effect without a controlled fixation comparison (standard IHC practice).
Should CPSF6 appear outside the nucleus in chromogenic IHC?
Use predominantly nuclear staining as the starting expectation: tissue IHC reports ubiquitous nuclear expression, while subcellular imaging places CPSF6 in the nucleoplasm and nuclear speckles (HPA tissue IHC; HPA subcellular). UniProt also describes cytoplasmic localisation and shuttling between nucleus and cytoplasm, so a cytoplasmic component merits investigation rather than automatic rejection (UniProt Q16630). Compare nuclear and cytoplasmic staining within the same intact cells, and verify that the DAB signal follows cell boundaries on a counterstained section (standard IHC practice). Recheck diffuse cytoplasmic colour against a no-primary control and areas of tissue damage before assigning it to CPSF6 (standard IHC practice). Paraffin IHC cannot by itself resolve individual nuclear speckles (standard IHC practice).
How do isoforms and epitope location affect CPSF6 IHC interpretation?
CPSF6 has 3 annotated isoforms and an RNA recognition motif at residues 81–161, but the supplied antibody evidence does not identify the recognised epitope (UniProt Q16630; datasheet A04551-1). Consequently, this IHC result cannot establish which isoform contributes to staining or whether all isoforms are detected (UniProt Q16630; datasheet A04551-1). CPSF6 also has annotated phosphorylation sites, including residues 157 and 494, without supplied evidence that those modifications alter this antibody’s staining (UniProt Q16630; datasheet A04551-1). If isoform specificity matters, seek epitope mapping or validate with an independently characterised antibody and an appropriate perturbation control (standard IHC practice). Score compartment and intensity without assigning an isoform to individual stained cells (standard IHC practice).
How can IF help check a puzzling CPSF6 IHC pattern?
Use IF as an orthogonal localisation check when chromogenic IHC gives ambiguous nuclear or cytoplasmic signal (standard IHC practice). Pair CPSF6 with a marker for the cell type being assessed and a nuclear counterstain, then examine whether the candidate signal occupies the expected cells and nuclei (HPA tissue IHC; standard IF practice). Select spectrally separated fluorophores and favour a far-red channel when tissue autofluorescence obscures shorter-wavelength signals, with single-label controls for multiplex interpretation (standard IF practice). CPSF6 is described in the nucleoplasm and nuclear speckles and has no transmembrane segment, so permeabilisation should allow antibody access to intracellular nuclear epitopes (HPA subcellular; UniProt Q16630; standard IF practice). Compare any punctate pattern with the reported nuclear distribution rather than treating every bright spot as specific (HPA subcellular; standard IF practice).
What should I check when DAB appears throughout the section?
First inspect a section without primary antibody to identify colour produced by the detection system or tissue rather than antibody binding (standard IHC practice). The selected procedure used biotinylated goat anti-rabbit secondary antibody, a streptavidin–biotin complex and DAB, so evaluate background at each detection stage when possible (datasheet A04551-1; standard IHC practice). Apply an appropriate endogenous peroxidase block and assess whether endogenous biotin contributes signal with this detection format (standard IHC practice). The caption reports a 10% goat serum block and 2 μg/ml primary antibody overnight at 4°C; use these as documented starting conditions when troubleshooting (datasheet A04551-1). Judge improvements by cleaner nuclear contrast in intact cells, consistent with the reported tissue pattern (HPA tissue IHC; standard IHC practice).
How should I quantify CPSF6 staining across paraffin sections? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and count only morphologically intact, evaluable nuclei within matched tissue regions (standard IHC practice). Report either the percentage of CPSF6-positive nuclei or a nuclear H-score that combines the percentage of cells at each staining intensity; state the scoring thresholds before analysis (standard IHC practice). Normalise counts to the number of evaluable cells, or report positive-cell density per mm² of analysed tissue when cellularity varies (standard IHC practice). Keep section processing, retrieval at pH 8.0, imaging and scoring rules consistent across samples (datasheet A04551-1; standard IHC practice). Record cytoplasmic staining separately because the reference tissue pattern is nuclear, although cytoplasmic localisation is also annotated (HPA tissue IHC; UniProt Q16630).
How can I separate genuine CPSF6 staining from tissue artefact?
A credible result has staining centred on intact nuclei across evaluable cells, consistent with the reported ubiquitous nuclear tissue pattern and nucleoplasmic localisation (HPA tissue IHC; HPA subcellular). Compare any cell-type difference with morphology and a suitable cell marker before calling it biologically selective, because tissue RNA specificity is reported as low (HPA tissue IHC; standard IHC practice). Treat staining restricted to section edges, folds or necrotic areas as suspect until it persists in well-preserved regions (standard IHC practice). Check a no-primary section and the peroxidase block when DAB appears in compartments inconsistent with the expected nuclear pattern (HPA tissue IHC; standard IHC practice). Interpret a reproducible cytoplasmic component cautiously because CPSF6 shuttling is annotated, while this IHC pattern alone does not establish its mechanism (UniProt Q16630; standard IHC practice).
Boster reagents
Best CPSF6 / Cleavage and polyadenylation specificity factor subunit 6 IHC Antibodies
Two anti-CPSF6 antibodies have human paraffin-section IHC figures and cell-based IF/ICC figures (catalog image captions). Catalog reactivity includes human, monkey, mouse, and rat (catalog reactivity).
Real IHC data
Anti-CPSF6 Antibody ®
Cat # A04551-1
Real IHC data
Anti-CPSF6 Antibody ® (monoclonal, 3F11E1)
Cat # M04551
A04551-1 has IHC images from human liver cancer and appendiceal adenocarcinoma paraffin sections, plus an IF/ICC image from MCF-7 cells (A04551-1 image captions). M04551 has IHC images from human squamous cell carcinoma, cervical cancer, colorectal adenocarcinoma, and ovarian cancer paraffin sections, plus an IF/ICC image from U20S cells (M04551 image captions).
Which to pick: For tissue IHC, A04551-1 is a rabbit antibody shown on human liver cancer paraffin sections, while M04551 is a mouse monoclonal, clone 3F11E1, shown on human squamous cell carcinoma paraffin sections; both captions use EDTA retrieval at pH 8.0 and 2 μg/ml primary antibody, and neither reports the fixative (catalog host/clone; A04551-1 and M04551 IHC captions). For IF/ICC, either SKU has a cell-based image and a listed concentration of 5 μg/ml; choose according to the rabbit or mouse secondary antibody available (catalog IF/ICC applications and IF captions). For work across species, both list human, monkey, mouse, and rat reactivity, while their pictured tissue IHC examples are human (catalog reactivity; A04551-1 and M04551 IHC captions).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q16630 (CPSF6_HUMAN, Cleavage and polyadenylation specificity factor subunit 6).
- Human Protein Atlas. CPSF6 tissue IHC expression (reliability: Supported).
- Human Protein Atlas. CPSF6 subcellular location (ICC-IF): Localized to the nucleoplasm and nuclear speckles..
- Human Protein Atlas. CPSF6 antibody validation summary (1 antibodies).
- Negative Regulation of CPSF6 Suppresses the Warburg Effect and Angiogenesis Leading to Tumor Progression Via c-Myc Signaling Network: Potential Therapeutic Target for Liver Cancer Therapy. International journal of biological sciences 2024 — PMC11234225.
- CPSF6 is a Clinically Relevant Breast Cancer Vulnerability Target: Role of CPSF6 in Breast Cancer. EBioMedicine 2017 — PMC5514498.
- IGF2BP2 binding to CPSF6 facilitates m6A-mediated alternative polyadenylation of PUM2 and promotes malignant progression in ovarian cancer. Clinical and translational medicine 2025 — PMC12238680.
- SNW1 promotes lymphatic metastasis in bladder cancer by modulating SRPK1 splicing. iScience 2026 — PMC12907903.
- PubMed PMID:9659921 — UniProt-cited evidence.
- PubMed PMID:14702039 — UniProt-cited evidence.
- PubMed PMID:15489334 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for CPSF6 (Cleavage and polyadenylation specificity factor subunit 6). Expected localisation Nuclear staining observed; cytoplasmic shuttling reported (HPA tissue IHC; UniProt). Antigen retrieval: EDTA pH 8.0 HIER, heat-mediated (datasheet A04551-1). Validated IHC antibody: A04551-1 at 2-5 μg/ml (the product's own IHC validation image is shown). Controls (HPA): positive Adipose tissue (Adipocytes); 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 liver cancer tissue; fixative not specified (datasheet A04551-1); 2. Fixation: Image fixative and duration unreported (datasheet A04551-1); 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 A04551-1); 20 min, 95–100 °C (standard); 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% goat serum (datasheet A04551-1); 8. Primary antibody: Rabbit anti-CPSF6, 2-5 μg/ml (datasheet A04551-1); 9. Primary incubation: Overnight at 4 °C (datasheet A04551-1). Watch for: Fixation: Matched tissue-IHC evidence does not establish the fixation claim. Validate the specimen-specific method before use. (selected-SKU IHC image A04551-1); Caveat: Nuclear–cytoplasmic shuttling may alter the pattern (UniProt); Isoform / epitope: 3 isoforms; verify antibody epitope coverage (UniProt); Regulation: No expression regulator annotated (UniProt). Evidence: UniProt Q16630, HPA tissue IHC · Supported, HPA ICC-IF · nucleoplasm and nuclear speckles., Datasheet A04551-1, PMC11234225, PMC5514498. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/CPSF6/immunohistochemistry-ihc-guide.