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BRF1 / Transcription factor IIIB 90 kDa subunit · IHC design guide
Design Immunohistochemistry for BRF1
Plan BRF1 chromogenic IHC in paraffin sections around its variable nuclear staining pattern (HPA tissue IHC). Use the IHC-validated antibody and compare positive tissue with a negative control, while checking for off-target staining (HPA tissue IHC; datasheet).
Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use
BRF1 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 in most tissues (HPA tissue IHC) | |
| Staining pattern | Variable nuclear staining across most tissues (HPA tissue IHC) | |
| Antigen retrieval | Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen) | |
| Positive control | Adrenal gland+4 more · see all | |
| Negative control | Adipose tissue+4 more · see all |
Important caveats
Reasons your staining may differ from the expected pattern.
| Fixation | Keep fixation consistent across sections. (standard IHC practice; not target-specific) | |
| Caveat | Presumed off-target binding may confound staining (HPA tissue IHC) | |
| Regulation | Staining intensity varies by tissue (HPA tissue IHC) | |
| Isoform / epitope | 9 isoforms; epitope coverage is undetermined (UniProt; datasheet) |
Section 1
Recommended BRF1 IHC & IF Protocols
The catalog antibody’s IHC-P protocol is accompanied by four published BRF1 IHC protocols (PMC8081602; PMC4868753; PMC7336232; PMC11369479).
| Sample | Paraffin-embedded human brain tissue; fixative not specified (datasheet A03761-1) |
| Fixation | Image fixative and duration unreported (datasheet A03761-1); verify before use. |
| Sectioning | 4–5 µm sections on charged slides (standard) |
| Deparaffinisation | Xylene, graded ethanol series to water (standard) |
| Antigen retrieval | Heat-induced epitope retrieval in Tris-EDTA buffer, pH 9.0, 20 min at 95–98 °C (standard rule: nuclear antigen) |
| Peroxidase block | 3% H2O2, 10 min, room temperature (standard) |
| Blocking | 10% normal serum of the secondary host, 30 min, room temperature (standard) |
| Primary antibody | Rabbit monoclonal (clone 2F1) anti-BRF1, 1:100-1:300 (datasheet A03761-1) |
| Primary incubation | Overnight at 4 °C (standard) |
| Detection | HRP-polymer secondary, DAB chromogen 5–10 min (standard) |
| Counterstain | Hematoxylin, blue, dehydrate and mount (standard) |
| Expected result | BRF1-positive staining in glandular cells of adrenal gland (HPA tissue IHC: High). HPA tissue profile: Nuclear expression of varying levels in most tissues. No signal in the no-primary control. |
💡Decision noteStart with Tris-EDTA retrieval at pH 9.0, 95–98 °C for 20 min (page retrieval rule: nuclear BRF1); compare citrate retrieval where reported (PMC4868753; PMC7336232).
Section 2
What Is the Expected BRF1 Staining Pattern?
BRF1 is a nuclear transcription factor with no annotated transmembrane segment (UniProt Q92994: subcellular location, function, topology). In paraffin-section IHC, expect nuclear staining of varying intensity across most tissues, including high staining in kidney tubular cells, cerebral-cortex neurons and testicular spermatogonia (HPA: tissue IHC). HPA rates its tissue pattern Approved, while noting presumed off-target binding was disregarded and external verification is pending (HPA: tissue IHC reliability).
| Nuclear staining in kidney tubules, cerebral-cortex neurons or testicular spermatogonia. | This matches HPA’s High cell-level staining in those tissues and BRF1’s nuclear location (HPA: tissue IHC; UniProt Q92994: subcellular location). Assess nuclei within the named cell population rather than calling an entire section uniformly positive (HPA: tissue IHC). |
| Predominantly cytoplasmic, membranous or extracellular staining, with little nuclear signal. | That distribution conflicts with the expected nuclear pattern and lack of an annotated transmembrane segment (UniProt Q92994: subcellular location, topology; HPA: tissue IHC). Treat it as suspect until controls and staining conditions are reviewed; location alone cannot identify the artefact’s cause (general IHC interpretation). |
| Strong staining in an HPA-listed cell population reported as Not detected, such as adipocytes or prostate glandular cells. | It differs from HPA’s observed cell-level result, so consider nonspecific antibody binding or endogenous chromogen-generating activity (HPA: tissue IHC; general chromogenic IHC practice). A single discordant section does not establish cross-reactivity; review controls and tissue identity (general IHC interpretation). |
| Diffuse staining across nuclei and surrounding tissue, obscuring cell boundaries. | The distribution cannot be scored confidently against HPA’s cell-specific nuclear pattern (HPA: tissue IHC). Excess primary-antibody signal, incomplete blocking or endogenous detection activity are general IHC possibilities; control sections help distinguish them (general chromogenic IHC practice). |
| No nuclear signal in a correctly identified, well-preserved HPA High cell population. | The result is discordant with that reported positive population (HPA: tissue IHC). Check the assay and positive-control section before interpreting the study tissue as BRF1-negative (general IHC practice). HPA’s Approved rating still carries a pending-external-verification caveat (HPA: tissue IHC reliability). |
💡Expected BRF1 appearanceCall a result positive when the relevant cells show discernible nuclear staining, potentially strong in HPA High populations; staining confined mainly to cytoplasm or to an HPA Not detected cell population is suspect (HPA: tissue IHC; UniProt Q92994: subcellular location).
| Which cells provide a useful comparison? | HPA reports High nuclear staining in kidney tubules, cerebral-cortex neurons, testicular spermatogonia and several other named populations; it reports Not detected in adipocytes and prostate glandular cells (HPA: tissue IHC). These are cell-level observations, and staining varies across tissues (HPA: tissue IHC profile). |
| How secure is the IHC pattern? | The tissue-IHC profile is Approved, with presumed off-target binding disregarded and external verification pending (HPA: tissue IHC reliability). HPA074990 has an Approved IHC entry; the supplied record does not label its IHC validation Enhanced (HPA: antibodies). |
| Can IF/ICC inform the expected compartment? | Yes: HPA reports approved nucleoplasm and nuclear-body localization in ICC-IF (HPA: subcellular ICC-IF). This supports looking for nuclear signal, while the paraffin-section pattern should be judged against tissue IHC (HPA: tissue IHC). HPA051918 has Approved ICC status; that record alone does not establish its IHC performance (HPA: antibodies). |
| Could isoforms affect interpretation? | UniProt lists nine BRF1 isoforms with distinct reported transcription roles for isoforms 1 and 2 (UniProt Q92994: isoforms, function). The supplied sources do not map an IHC antibody epitope to those isoforms; avoid assigning an observed tissue-staining difference to a particular isoform (UniProt Q92994: isoforms; HPA: antibodies). |
| What can antigen retrieval establish here? | Retrieval conditions can be optimized against a positive-control section as general paraffin-IHC practice. The supplied UniProt and HPA records give no BRF1-specific retrieval or fixation-sensitivity result, so a change in staining after optimization cannot, by itself, establish a BRF1-specific fixation effect. |
| Situation | Likely cause | Next action |
|---|---|---|
| Kidney tubular nuclei are unstained while the section otherwise appears usable. | This conflicts with HPA’s High staining in tubular cells; an assay failure or a mismatch between the scored cells and reference population is possible (HPA: tissue IHC; general IHC interpretation). | Confirm tubular-cell identity, examine a same-run positive control, then review antibody dilution, retrieval and detection steps as general paraffin-IHC checks. Avoid declaring BRF1 absent from the study tissue until the positive control works (general IHC practice). |
| Color is strongest outside nuclei, including at cell edges. | The compartment conflicts with BRF1’s nuclear annotation and HPA’s nuclear tissue profile (UniProt Q92994: subcellular location; HPA: tissue IHC). The pattern does not pinpoint a single technical cause (general IHC interpretation). | Compare a no-primary control and the positive-control tissue, inspect morphology, and review blocking and detection steps (general chromogenic IHC practice). Score only interpretable nuclear signal against the named cell population (HPA: tissue IHC). |
| An HPA Not detected cell population stains strongly. | The result is discordant with HPA’s cell-level observation and could reflect nonspecific binding or endogenous detection activity (HPA: tissue IHC; general chromogenic IHC practice). | Verify cell identity and compare no-primary and detection controls (general IHC practice). Keep the discrepancy explicit: HPA’s Approved tissue profile notes presumed off-target binding was disregarded and external verification is pending (HPA: tissue IHC reliability). |
| Nearly every structure has diffuse brown signal. | Widespread signal obscures the nuclear, cell-specific pattern needed for interpretation (HPA: tissue IHC). Incomplete blocking, excessive primary-antibody signal or endogenous detection activity are general IHC possibilities. | Use a no-primary control to assess background, then review blocking, antibody dilution, washing and chromogen development against the positive-control section (general chromogenic IHC practice). Reassess only after nuclei can be distinguished. |
| Only faint signal appears in a tissue expected to stain strongly. | HPA’s High label refers to specified cells, not every cell in that tissue (HPA: tissue IHC). A weak field can reflect cell selection or assay performance; the supplied sources do not establish a BRF1-specific fixation effect. | Identify the HPA-listed cell population, compare it with a same-run positive control, and review retrieval and detection as general paraffin-IHC steps (HPA: tissue IHC; general IHC practice). |
| ICC-IF shows nuclear bodies, while chromogenic tissue IHC looks broadly nuclear. | HPA reports nucleoplasm and nuclear bodies by ICC-IF, and a nuclear tissue-IHC profile (HPA: subcellular ICC-IF; HPA: tissue IHC). These observations use different preparations and readouts; the supplied sources do not require nuclear bodies to resolve in chromogenic tissue sections. | Use the IF/ICC result to check nuclear compartment, then score the paraffin section by its tissue-IHC cell population and nuclear signal (HPA: subcellular ICC-IF; HPA: tissue IHC). Do not treat unresolved nuclear bodies alone as an IHC failure. |
Experiment evidence
IHC & IF images showing BRF1 staining
A03761-1 · IHCImmunohistochemistry analysis of paraffin-embedded human brain tissue, using TF3B Antibody. The picture on the right is blocked with the syn
A03761-1 · IFImmunofluorescence analysis of MCF7 cells, using TF3B Antibody. The picture on the right is blocked with the synthesized peptide.
A30544 · IHCImmunohistochemistry analysis of paraffin-embedded human brain tissue, using TF3B Antibody. The picture on the right is blocked with the syn
A30544 · IFImmunofluorescence analysis of MCF7 cells, using TF3B Antibody. The picture on the right is blocked with the synthesized peptide.
HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000185024-BRF1/tissue/cerebral+cortex#imid_20575955
HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000185024-BRF1/tissue/colon#imid_20575881
HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000185024-BRF1/tissue/liver#imid_20575882
HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000185024-BRF1/tissue/kidney#imid_20575875
HPA · ICC-IF MCF-7Human Protein Atlas immunofluorescence, MCF-7, antibody HPA051918; green = BRF1, blue = nucleus, red = microtubules.
HPA · ICC-IF MCF-7Human Protein Atlas immunofluorescence, MCF-7, antibody HPA051918; green = BRF1, blue = nucleus, red = microtubules.
← swipe / scroll for more images →
Real IHC / IF data behind the staining-pattern expectations in this section.
Sample controls for BRF1 IHC & IF
🧪Run testis first: spermatogonia should show nuclear staining because HPA rates them High (HPA: High in testis spermatogonia; UniProt Q92994: nucleus). Use prostate glandular cells as a negative tissue because HPA lists them as Not detected (HPA: Not detected in prostate glandular cells); HPA identifies no internal negative cell population in testis, so only cells independently verified as BRF1-negative should be expected to lack specific nuclear staining (HPA: testis row).
Positive control tissue: Adrenal gland (Glandular cells, HPA High)
Negative control tissue: Adipose tissue (HPA Not detected)
ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show BRF1 in MCF-7, PC-3, U2OS, NIH 3T3, with annotated localisation: Nucleoplasm (approved), Nuclear bodies (approved) (HPA subcellular).
Technical controls: Include a no-primary (secondary-only) slide, an isotype control matched to the primary antibody’s host species and immunoglobulin class, and a BRF1 knockout control where available (standard IHC control practice). Peptide blocking is also documented for the catalog antibody’s paraffin-section image (catalog antibody A03761-1 caption); for chromogenic HRP detection, quench endogenous peroxidase and check endogenous biotin if using an avidin–biotin system (standard IHC practice).
⚠️Feasibility: A target-specific fixation window and fixation effect are unreported; the selected-SKU paraffin-section caption does not state a fixative (catalog antibody A03761-1 caption). Antigen-retrieval dependence is unreported, so optimize retrieval on the positive and negative tissues; the supplied evidence does not establish that frozen sections or IF are easier (catalog antibody A03761-1 caption; HPA: tissue rows). In testis, score nuclear staining in spermatogonia and distinguish it from nonspecific chromogen or endogenous enzyme signal (HPA: High in testis spermatogonia; UniProt Q92994: nucleus; standard IHC practice).
HPA tissue IHC evidence for BRF1
Comprehensive Human Protein Atlas IHC scoring per tissue (reliability: Approved — Presumed off target binding observed and disregarded. Pending external verification.). 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 → |
| Cerebral cortex | Neuronal cells | High | Protein (IHC) | HPA → |
| Endometrium | Cells in endometrial stroma | High | Protein (IHC) | HPA → |
| Kidney | Cells in tubules | High | Protein (IHC) | HPA → |
| Testis | Spermatogonia cells | High | Protein (IHC) | HPA → |
Undetected expression · recommended negative controls
| Tissue | Cell type | Level | Evidence | Source |
|---|---|---|---|---|
| Adipose tissue | Adipocytes | Not detected | Protein (IHC) | HPA → |
| Liver | Cholangiocytes | Not detected | Protein (IHC) | HPA → |
| Ovary | Ovarian stroma cells | Not detected | Protein (IHC) | HPA → |
| Parathyroid gland | Glandular cells | Not detected | Protein (IHC) | HPA → |
| Prostate | Glandular cells | Not detected | Protein (IHC) | HPA → |
Section 3
Advanced BRF1 IHC Tips
Troubleshoot BRF1 staining by checking nuclear localisation, cell type, section quality and controls before interpreting chromogenic signal.
How should I adjust retrieval when BRF1 nuclear staining is weak?
Use Tris-EDTA pH 9.0 HIER at 95–98 °C for 20 min (page setting: nuclear-antigen rule). Let sections cool in retrieval buffer, then compare nuclear staining with a matched section processed in the same run; BRF1 is a nuclear protein (UniProt Q92994: subcellular location). If staining remains weak, check deparaffinisation and whether the heating bath reached its set temperature before extending retrieval time, since excessive retrieval can damage morphology (standard IHC practice). Judge improvement by clearer nuclear signal with intact nuclei, rather than by increased staining throughout the section (HPA: nuclear expression in most tissues).
Could fixation explain weak BRF1 staining in paraffin sections?
Target-specific sensitivity of BRF1 staining to fixative choice or fixation duration is unknown from the supplied evidence (selected A03761-1 caption: fixative not stated). The catalog image documents staining in paraffin-embedded human brain tissue, but reports no fixation conditions (selected A03761-1 caption). When investigating weak staining, compare sections with documented processing histories using the same retrieval and detection run; differences in fixation can alter antigen accessibility in routine IHC (standard IHC practice). Record fixation conditions, section age and nuclear morphology alongside staining, and avoid assigning a BRF1-specific fixation effect from tissue staining patterns alone (HPA: tissue IHC profile; standard IHC practice).
Should I count cytoplasmic staining as BRF1 positive?
Score nuclear staining as the expected BRF1 pattern: UniProt places BRF1 in the nucleus, while HPA reports nucleoplasm and nuclear bodies (UniProt Q92994: subcellular location; HPA: approved subcellular locations). Use a nuclear counterstain to check whether chromogen overlies intact nuclei, especially where crowded cells make compartments hard to separate (standard IHC practice). Predominantly cytoplasmic or membrane staining warrants review of background and antibody specificity; BRF1 has no annotated transmembrane segment (UniProt Q92994: topology). Keep compartment-specific scores separate, and compare the disputed pattern with a control section from the same staining run before calling it positive (standard IHC practice).
Can this antibody distinguish BRF1 isoforms or phosphorylation states in IHC?
Do not assign staining to a particular BRF1 isoform without epitope mapping and isoform-specific validation: the supplied record lists 9 isoforms, but gives no antibody epitope (UniProt Q92994: isoforms; supplied antibody evidence). Isoform 1 and isoform 2 have different reported transcriptional roles, so total staining cannot establish which role predominates in a section (UniProt Q92994: function). BRF1 also has annotated phosphorylation sites, including residues 365, 450 and 553 (UniProt Q92994: modified residues). Peptide blocking in the catalog brain image supports competition by that peptide, but does not establish isoform or phosphorylation specificity (selected A03761-1 caption).
How can IF help verify BRF1 localisation alongside a cell-type marker?
On the separate IF/ICC workflow, pair BRF1 with a validated marker for the cell type being examined and a nuclear stain, then inspect whether BRF1 occupies the nucleoplasm or nuclear bodies (HPA: approved subcellular locations; standard IF practice). Select spectrally separated fluorophores and measure unstained tissue autofluorescence before choosing the BRF1 channel, particularly when broad background obscures nuclei (standard IF practice). BRF1 has no transmembrane segment and is nuclear, so use controlled permeabilisation to allow antibody access to its intracellular epitope; the precise antibody epitope is not supplied (UniProt Q92994: topology and location; supplied antibody evidence). Include single-channel controls to assess bleed-through (standard IF practice).
What should I check when BRF1 chromogenic staining is diffuse?
First separate nuclear signal from diffuse chromogen using a nuclear counterstain; expected BRF1 staining is nuclear (UniProt Q92994: subcellular location; HPA: tissue IHC profile). Review a no-primary control for secondary-reagent background, and check the peroxidase block when using enzyme-based detection (standard chromogenic IHC practice). Compare damaged edges, folds and poorly preserved areas with intact tissue before changing the primary-antibody concentration; these areas can trap reagents or stain unevenly (standard IHC practice). The selected catalog image includes peptide-blocked human brain tissue, but peptide competition alone does not exclude every off-target pattern (selected A03761-1 caption; HPA: presumed off-target binding observed).
How should I quantify BRF1 across sections with different cell mixtures? ⚠ ANSWER MARKED FOR VERIFICATION
Define the cell population and scoring region before counting, then report the percentage of nuclei judged positive and, where intensity is reproducible, a nuclear H-score (standard IHC quantification practice; UniProt Q92994: nuclear location). Normalise positive counts to all eligible nuclei in that population, and state the number of evaluable cells or sampled area for each section (standard IHC quantification practice). Keep cell populations separate because HPA reports varying nuclear levels across most tissues, including high staining in cerebral cortex neuronal cells and undetected staining in adipocytes (HPA: tissue IHC profile). Apply identical thresholds and exclude damaged or necrotic regions consistently across slides (standard IHC practice).
How do I distinguish genuine BRF1 staining from an artefact?
A credible positive pattern is nuclear staining in intact cells, consistent with BRF1's nuclear location and HPA's nucleoplasmic and nuclear-body observations (UniProt Q92994: subcellular location; HPA: approved subcellular locations). Check whether the stained cell population fits the tissue context; HPA reports high staining in kidney tubular cells, for example, but also notes presumed off-target binding in its IHC assessment (HPA: tissue IHC profile and reliability description). Discount isolated edge staining, necrotic areas and signal reproduced in a no-primary control, and assess endogenous peroxidase when using chromogenic detection (standard IHC practice). The catalog peptide-blocked image adds supporting evidence for the displayed pattern, not proof of universal specificity (selected A03761-1 caption).
Boster reagents
Best BRF1 / Transcription factor IIIB 90 kDa subunit IHC Antibodies
Two anti-BRF1 antibodies have IHC images from human brain paraffin sections and IF images from MCF7 cells (each SKU’s image captions); both list human and mouse reactivity (catalog reactivity).
Real IHC data
Anti-TFIIIB90-1 Antibody
Cat # A03761-1
Real IHC data
Anti-TF3B BRF1 Antibody
Cat # A30544
A03761-1 lists IHC and IF, with its own human brain paraffin-section IHC image and MCF7-cell IF image (catalog applications; A03761-1 image captions). A30544 lists IHC, IF and ICC, with its own human brain paraffin-section IHC image and MCF7-cell IF image (catalog applications; A30544 image captions).
Which to pick: For tissue IHC, either A03761-1 (clone 2F1) or A30544 (polyclonal) has its own human brain paraffin-section image; neither caption reports the fixative (catalog clone/type; each SKU’s IHC image caption). Choose A30544 if an explicit ICC application listing matters; both list IF and show MCF7-cell IF images (catalog applications; each SKU’s IF image caption). Both list human and mouse reactivity, while the supplied IHC images show human tissue only (catalog reactivity; each SKU’s IHC image caption).
Each figure is that product's own IHC / IF validation image from its datasheet.
References
- UniProt Consortium. UniProt entry Q92994 (TF3B_HUMAN, Transcription factor IIIB 90 kDa subunit).
- Human Protein Atlas. BRF1 tissue IHC expression (reliability: Approved).
- Human Protein Atlas. BRF1 subcellular location (ICC-IF): Localized to the nucleoplasm and nuclear bodies..
- Human Protein Atlas. BRF1 antibody validation summary (2 antibodies).
- Exploring the Role and Mechanism of pAMPKα-Mediated Dysregulation of Brf1 and RNA Pol III Genes. Oxidative medicine and cellular longevity 2021 — PMC8081602.
- The significance of Brf1 overexpression in human hepatocellular carcinoma. Oncotarget 2016 — PMC4868753.
- Mitogen- and Stress-Activated Protein Kinase 1 Mediates Alcohol-Upregulated Transcription of Brf1 and tRNA Genes to Cause Phenotypic Alteration. Oxidative medicine and cellular longevity 2020 — PMC7336232.
- BRF1 promotes the odontogenic differentiation of dental pulp stem cells in pulpitis by inducing autophagy. Heliyon 2024 — PMC11369479.
- PubMed PMID:7624363 — UniProt-cited evidence.
- PubMed PMID:8943358 — UniProt-cited evidence.
- PubMed PMID:10921893 — UniProt-cited evidence.
Immunohistochemistry protocol sheet for BRF1 (Transcription factor IIIB 90 kDa subunit). Expected localisation Nuclear staining in most tissues (HPA tissue IHC). Antigen retrieval: Tris-EDTA pH 9.0 HIER, 95–98 °C, 20 min (rule: nuclear antigen). Validated IHC antibody: A03761-1 at 1:100-1:300 (the product's own IHC validation image is shown). Controls (HPA): positive Adrenal gland (Glandular cells); negative Adipose tissue. IHC-P workflow on paraffin sections; fixative unspecified. Protocol steps: 1. Sample: Paraffin-embedded human brain tissue; fixative not specified (datasheet A03761-1); 2. Fixation: Image fixative and duration unreported (datasheet A03761-1); 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-induced epitope retrieval in Tris-EDTA buffer, pH 9.0 , 20 min at 95–98 °C…; 6. Peroxidase block: 3% H2O2, 10 min , room temperature (standard); 7. Blocking: 10% normal serum of the secondary host, 30 min , room temperature (standard); 8. Primary antibody: Rabbit monoclonal (clone 2F1) anti-BRF1, 1:100-1:300 (datasheet A03761-1); 9. Primary incubation: Overnight at 4 °C (standard). Watch for: Fixation: Keep fixation consistent across sections. (standard IHC practice; not target-specific); Caveat: Presumed off-target binding may confound staining (HPA tissue IHC); Isoform / epitope: 9 isoforms; epitope coverage is undetermined (UniProt; datasheet); Regulation: Staining intensity varies by tissue (HPA tissue IHC). Evidence: UniProt Q92994, HPA tissue IHC · Approved, HPA ICC-IF · nucleoplasm and nuclear bodies., Datasheet A03761-1, PMC8081602, PMC4868753. QR code links to https://www.bosterbio.com/bosterbio-gene-info-cards/BRF1/immunohistochemistry-ihc-guide.