MCM3 / DNA replication licensing factor MCM3 · IHC design guide

Design Immunohistochemistry for MCM3

Plan MCM3 paraffin IHC around nuclear staining in proliferating cells (HPA tissue IHC). Bone marrow hematopoietic cells offer a high-expression reference, while adipocytes are reported as not detected (HPA tissue IHC).

Evidence assembled Oct 2026 · For research use; verify linked source records and product datasheet before use

Immunohistochemistry protocol sheet for MCM3 (IHC for MCM3): expected localisation Nuclei of proliferating cells (HPA tissue IHC), antibody PA1651, validated IHC image, and IHC protocol steps — Printable **MCM3** IHC protocol sheet — expected localisation Nuclei of proliferating cells (HPA tissue IHC), antibody PA1651, controls and protocol steps. Open the full MCM3 IHC guide →

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MCM3 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	Nuclei of proliferating cells (HPA tissue IHC)
	Staining pattern	High nuclear signal in marrow hematopoietic cells (HPA tissue IHC)
	Antigen retrieval	EDTA pH 8.0 HIER, heat-mediated (datasheet PA1651)
	Positive control ⓘ	Bone marrow+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	Proliferation varies within tissue, changing the positive-cell fraction (HPA tissue IHC)
	Regulation	Enriched in proliferating cells (HPA tissue IHC)
	Isoform / epitope	2 isoforms; epitope differences are unspecified (UniProt)

Section 1

Recommended MCM3 IHC & IF Protocols

Compare the catalog antibody’s IHC-P protocol (datasheet: PA1651) with published breast biopsy, melanoma, and ovarian carcinoma IHC methods (PMC12534050; PMC3433373; PMC9035053).

Recommended immunohistochemistry (IHC-P) protocol parameters
Sample	Paraffin-embedded human cervical cancer tissue; fixative not specified (datasheet PA1651)
Fixation	Image fixative and duration unreported (datasheet PA1651); 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 PA1651); 20 min, 95–100 °C (standard)
Peroxidase block	3% H2O2, 10 min, room temperature (standard)
Blocking	10% goat serum (datasheet PA1651)
Primary antibody	Rabbit anti-MCM3, 2-5μg/ml (datasheet PA1651)
Primary incubation	Overnight at 4 °C (datasheet PA1651)
Detection	HRP-conjugated secondary, DAB chromogen (datasheet PA1651)
Counterstain	Hematoxylin, blue, dehydrate and mount (standard)
Expected result	MCM3-positive staining in hematopoietic cells of bone marrow (HPA tissue IHC: High). HPA tissue profile: Nuclear expression in proliferating cells. No signal in the no-primary control.

💡Decision noteStart with heat-mediated EDTA pH 8.0 retrieval for the catalog antibody (datasheet: PA1651), then assess nuclear staining with tissue controls (UniProt: P25205 nucleus).

Section 2

What Is the Expected MCM3 Staining Pattern?

MCM3 should stain nuclei, especially in proliferating cells (HPA tissue IHC: nuclear expression in proliferating cells; UniProt P25205: nucleus and chromosome). High staining is reported in bone marrow hematopoietic cells and placental cytotrophoblasts (HPA tissue IHC). The tissue pattern has Supported reliability, with medium consistency between staining and RNA data (HPA tissue IHC). MCM3 has no transmembrane segment (UniProt P25205 topology).

What am I looking at on my slide?
Distinct nuclear staining in bone marrow hematopoietic cells or placental cytotrophoblasts.	This fits the reported high staining in both cell populations and the expected nuclear location (HPA tissue IHC; UniProt P25205). Judge the named cells, rather than calling every cell in the section positive. Staining strength elsewhere may differ: skin basal-layer cells and lymph-node germinal-center cells are reported at medium levels (HPA tissue IHC).
Predominantly cytoplasmic staining, with little convincing nuclear staining.	Treat this as a possible assay artefact because the reported tissue pattern is nuclear and the approved ICC-IF location is nucleoplasmic (HPA tissue IHC; HPA subcellular). Review a known-positive section and a control omitting the primary antibody. Chromatin association changes during replication, so a single cell’s appearance alone is insufficient to define a new compartment pattern (UniProt P25205).
Strong staining in adipocytes or adrenal glandular cells.	These particular cell populations were reported as not detected (HPA tissue IHC); staining there merits a cross-reactivity or endogenous-detection check. The HPA designation applies to those named cells, not every cell in adipose tissue or adrenal gland. Compare nuclear morphology and a control omitting the primary antibody before interpreting unexpected color as MCM3.
Diffuse color covers tissue, including spaces between cells.	Diffuse, noncellular color does not match nuclear expression in proliferating cells (HPA tissue IHC). As general IHC practice, assess blocking, antibody concentration, detection background and wash steps, then compare with a control omitting the primary antibody. This observation alone cannot identify which reagent or step caused the background.
No nuclear signal in bone marrow hematopoietic cells or placental cytotrophoblasts.	Absence conflicts with the reported high staining in those cell populations (HPA tissue IHC), but does not by itself prove that MCM3 is absent. First verify that the expected cells are present and assess the IHC-validated antibody and detection controls. The supplied sources do not establish a target-specific fixation sensitivity.

💡Expected MCM3 appearanceA convincing positive result is nuclear staining in the named proliferative populations, with reported high levels in bone marrow hematopoietic cells and placental cytotrophoblasts; widespread cytoplasmic or diffuse noncellular color is suspect (HPA tissue IHC; UniProt P25205).

How each factor affects the staining
Cell population and scoring region	MCM3 shows nuclear expression in proliferating cells (HPA tissue IHC). HPA reports high staining in bone marrow hematopoietic cells and placental cytotrophoblasts, medium staining in skin basal-layer cells, and no detection in adipocytes (HPA tissue IHC). Score the specified cells and their nuclear signal; these entries do not assign one intensity to an entire tissue.
Replication-stage localization	MCM3 associates with chromatin before nuclei form and detaches as DNA replication progresses (UniProt P25205). Its reported locations are nucleus and chromosome (UniProt P25205), while HPA reports an approved nucleoplasmic ICC-IF location (HPA subcellular). Interpret unusual single-cell appearances in the context of the overall nuclear tissue pattern.
Antibody evidence and molecular variation	HPA lists three antibodies with Supported IHC status; CAB002162 also has Approved ICC status (HPA antibodies). Supported tissue reliability means medium consistency with RNA data, not proof that every stained cell is specific (HPA tissue IHC). UniProt lists two isoforms (UniProt P25205); no supplied epitope information establishes whether the catalog antibody detects both.
IF/ICC Q: Where should signal appear?	A: The approved ICC-IF main location is the nucleoplasm, with no additional location listed (HPA subcellular). HPA lists ICC-IF images for A-431, U-251MG and U2OS (HPA subcellular). This localization answer does not supply an IF/ICC protocol or establish that an IHC-P antibody dilution transfers to IF/ICC.

Why is my staining missing, weak or wrong?
Situation	Likely cause	Next action
High background obscures nuclear boundaries.	As general IHC practice, nonspecific antibody binding or detection-system background can produce diffuse color; the HPA pattern is nuclear (HPA tissue IHC).	As general IHC practice, compare with a control omitting the primary antibody, then review blocking, antibody concentration and washes. Keep assessment focused on resolved nuclei rather than total brown area.
Signal is mainly cytoplasmic.	This differs from the nucleus/chromosome annotation and the nuclear tissue pattern (UniProt P25205; HPA tissue IHC); the image alone cannot identify the cause.	As general IHC practice, inspect morphology and compare a known-positive section with a control omitting the primary antibody. Reassess the pattern before treating cytoplasmic color as MCM3.
No staining appears in a known-positive cell population.	Bone marrow hematopoietic cells and placental cytotrophoblasts are reported high (HPA tissue IHC); absence may reflect cell selection or an assay problem.	Confirm the named cells are present, then check antibody and detection controls using general IHC practice. Do not attribute failure specifically to fixation or antigen retrieval: target-specific effects are unreported in the supplied sources.
Unexpected cells stain strongly.	For adipocytes and adrenal glandular cells, HPA reports no detection (HPA tissue IHC); cross-reactivity or endogenous detection activity is possible, not established.	Compare the staining with nuclear morphology and a control omitting the primary antibody; as general IHC practice, assess endogenous detection activity if the control is colored. Interpret HPA's negative calls at the named-cell level.
Only a subset of nuclei stains.	HPA describes nuclear expression in proliferating cells, while UniProt describes a role in cell-cycle DNA replication (HPA tissue IHC; UniProt P25205). A mixed field need not stain uniformly.	Identify the cell populations and score their nuclear staining separately. Compare expected high and medium HPA populations before increasing assay sensitivity merely to make all nuclei positive (HPA tissue IHC).
IF/ICC and IHC images appear different.	HPA's approved ICC-IF location is nucleoplasmic, while tissue IHC reports nuclear expression in proliferating cells (HPA subcellular; HPA tissue IHC). The supplied records do not compare protocol performance.	Evaluate nuclear localization within each application. Use the separate IF/ICC guide for its workflow; do not transfer an IHC-P procedure or interpretation threshold to IF/ICC solely from these localization records.

Source: UniProt P25205 Human Protein Atlas tissue Human Protein Atlas subcellular

Experiment evidence

IHC & IF images showing MCM3 staining

IHC analysis of MCM3 using anti-MCM3 antibody (PA1651). MCM3 was detected in a paraffin-embedded section of human cervical cancer tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 2 μg/ml rabbit anti-MCM3 Antibody (PA1651) overnight at 4°C. Peroxidase Conjugated Goat Anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using HRP Conjugated Rabbit IgG Super Vision Assay Kit (Catalog # SV0002) with DAB as the chromogen.

PA1651 · IHCIHC analysis of MCM3 using anti-MCM3 antibody (PA1651). MCM3 was detected in a paraffin-embedded section of human cervical cancer tissue. He

IHC analysis of MCM3 using anti-MCM3 antibody (PA1651). MCM3 was detected in a paraffin-embedded section of human breast cancer tissue. Heat mediated antigen retrieval was performed in EDTA buffer (pH 8.0, epitope retrieval solution). The tissue section was blocked with 10% goat serum. The tissue section was then incubated with 2 μg/ml rabbit anti-MCM3 Antibody (PA1651) overnight at 4°C. Peroxidase Conjugated Goat Anti-rabbit IgG was used as secondary antibody and incubated for 30 minutes at 37°C. The tissue section was developed using HRP Conjugated Rabbit IgG Super Vision Assay Kit (Catalog # SV0002) with DAB as the chromogen.

PA1651 · IHCIHC analysis of MCM3 using anti-MCM3 antibody (PA1651). MCM3 was detected in a paraffin-embedded section of human breast cancer tissue. Heat

IF analysis of MCM3 using anti-MCM3 antibody (PA1651) and anti-Tubulin Alpha antibody (M03989-3). MCM3 was detected in immunocytochemical section of Hela cell. Enzyme antigen retrieval was performed using IHC enzyme antigen retrieval reagent (AR0022) for 15 mins. The cells were blocked with 10% goat serum. And then incubated with 5 μg/mL rabbit anti-MCM3 Antibody (PA1651) and mouse anti-Tubulin Alpha antibody (M03989-3) overnight at 4°C. DyLight®488 Conjugated Goat Anti-Rabbit IgG (BA1127) and Cy3 Conjugated Goat Anti-Mouse IgG (BA1031) were used as secondary antibody at 1:500 dilution and incubated for 30 minutes at 37°C. The section was counterstained with DAPI. Visualize using a fluorescence microscope and filter sets appropriate for the label used.

PA1651 · IFIF analysis of MCM3 using anti-MCM3 antibody (PA1651) and anti-Tubulin Alpha antibody (M03989-3). MCM3 was detected in immunocytochemical se

HPA · Cerebral cortexHuman Protein Atlas IHC, Cerebral cortex. Source: https://www.proteinatlas.org/ENSG00000112118-MCM3/tissue/cerebral+cortex#imid_700608

HPA · ColonHuman Protein Atlas IHC, Colon. Source: https://www.proteinatlas.org/ENSG00000112118-MCM3/tissue/colon#imid_700542

HPA · LiverHuman Protein Atlas IHC, Liver. Source: https://www.proteinatlas.org/ENSG00000112118-MCM3/tissue/liver#imid_700543

HPA · KidneyHuman Protein Atlas IHC, Kidney. Source: https://www.proteinatlas.org/ENSG00000112118-MCM3/tissue/kidney#imid_700544

HPA · ICC-IF A-431Human Protein Atlas immunofluorescence, A-431, antibody CAB002162; green = MCM3, blue = nucleus, red = microtubules.

← swipe / scroll for more images →

Real IHC / IF data behind the staining-pattern expectations in this section.

Sample controls for MCM3 IHC & IF

🧪Run bone marrow first and require nuclear staining in hematopoietic cells (HPA: High in hematopoietic cells; UniProt P25205: nucleus). Use adipose tissue as the negative tissue (HPA: adipocytes Not detected); within the bone marrow section, cells without nuclear chromogen signal provide internal contrast, although HPA does not designate a specific negative marrow cell type.

Positive control tissue: Bone marrow (Hematopoietic cells, HPA High)

Negative control tissue: Adipose tissue (HPA Not detected)

ICC-IF cell lines (HPA subcellular resource): HPA ICC-IF images show MCM3 in A-431, U-251MG, U2OS, with annotated localisation: Nucleoplasm (approved) (HPA subcellular).

Technical controls: Include a no-primary, secondary-only control and an irrelevant IgG control matched to the primary antibody’s host species and clonality; confirm specificity with MCM3 knockout material or a validated peptide block (standard IHC practice). Quench endogenous peroxidase in bone marrow before HRP/DAB detection (standard IHC practice; selected PA1651 caption: HRP/DAB).

⚠️Feasibility: A target-specific fixation window or fixation effect is unreported, and the selected PA1651 paraffin-section caption does not state a fixative. The caption demonstrates heat-mediated retrieval in EDTA at pH 8.0, but does not establish that retrieval is required (selected PA1651 caption). Relative ease of frozen-section IHC versus IF is unreported; ICC-IF does show nucleoplasmic localization (HPA: approved nucleoplasm).

HPA tissue IHC evidence for MCM3

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
Bone marrow	Hematopoietic cells	High	Protein (IHC)	HPA →
Placenta	Cytotrophoblasts	High	Protein (IHC)	HPA →
Duodenum	Enterocytes	Medium	Protein (IHC)	HPA →
Lymph node	Germinal center cells	Medium	Protein (IHC)	HPA →
Nasopharynx	Ciliated cells (cell body)	Medium	Protein (IHC)	HPA →

Undetected expression · recommended negative controls

Tissue	Cell type	Level	Evidence	Source
Adipose tissue	Adipocytes	Not detected	Protein (IHC)	HPA →
Adrenal gland	Glandular cells	Not detected	Protein (IHC)	HPA →
Appendix	Endocrine cells	Not detected	Protein (IHC)	HPA →
Bronchus	Basal cells	Not detected	Protein (IHC)	HPA →
Caudate	Glial cells	Not detected	Protein (IHC)	HPA →

Section 3

Advanced MCM3 IHC Tips

Troubleshoot MCM3 staining by checking nuclear localisation, tissue controls and detection background before interpreting the fraction of positive cells.

How should I retrieve MCM3 in paraffin sections when nuclear staining is weak?

Use heat mediated retrieval in EDTA at pH 8.0 first (datasheet PA1651). The PA1651 paraffin section example used this retrieval before overnight incubation at 4°C with 2 μg/ml primary antibody (datasheet PA1651). If nuclei remain weak, adjust heating duration in small steps while keeping buffer, antibody concentration and detection conditions fixed, and inspect tissue integrity after each change (standard IHC practice). Include a bone marrow hematopoietic cell or placental cytotrophoblast control, where staining is reported as high (HPA tissue IHC). Excessive retrieval can damage morphology or increase background, so assess the control and test sections together (standard IHC practice).

Could fixation explain weak MCM3 staining in my paraffin sections?

Target specific MCM3 fixation sensitivity is unknown from the supplied evidence; the PA1651 paraffin section caption does not report a fixative (datasheet PA1651). Record the fixative, fixation duration and tissue processing history for each case, then compare sections processed together using identical retrieval and staining conditions (standard IHC practice). If fixation varies, first check whether nuclei and overall morphology remain intact, and use a consistently processed positive control to assess staining performance (standard IHC practice). Do not attribute a weak result to a particular MCM3 modification or to its nuclear localisation without direct fixation comparisons (UniProt P25205; standard IHC practice).

What staining pattern should count as MCM3 positive in chromogenic IHC?

Score convincing nuclear staining in morphologically intact cells as the expected pattern (UniProt P25205 nucleus; HPA tissue IHC nuclear expression in proliferating cells). MCM3 is also associated with chromatin before nuclei form and detaches as DNA replication progresses, so nuclear intensity need not be uniform across cells (UniProt P25205 subcellular annotation). Inspect a matched counterstain to distinguish nuclear DAB from pigment or diffuse cytoplasmic colour, and keep the positivity threshold consistent across sections (standard IHC practice). Widespread isolated cytoplasmic staining should trigger checks of antibody concentration, washing and detection background before biological interpretation (UniProt P25205 nucleus; standard IHC practice).

Could isoforms or epitope accessibility explain inconsistent MCM3 IHC staining?

MCM3 has 2 annotated isoforms, but the supplied PA1651 caption does not identify its epitope or establish isoform coverage (UniProt P25205 isoforms; datasheet PA1651). It also lists multiple modified residues, including phosphorylation and acetylation, without showing whether they alter this antibody’s binding in paraffin sections (UniProt P25205 modified residues). Compare staining across serial sections with the same retrieval and detection settings before assigning regional differences to an isoform or modification (standard IHC practice). If an epitope map becomes available, check whether it lies in a sequence shared by the isoforms; document that check separately from observed IHC performance (standard IHC practice).

How can IF help assess an ambiguous nuclear MCM3 IHC pattern?

For a separate IF assessment, examine whether MCM3 signal overlaps nuclei, consistent with its approved nucleoplasmic location (HPA subcellular). Multiplex with a marker for the expected population, such as a validated hematopoietic cell marker in bone marrow, where hematopoietic cells show high MCM3 staining (HPA tissue IHC; standard IF practice). Choose fluorophores after checking tissue autofluorescence and include single stain controls to assess spectral bleed through (standard IF practice). Because the expected epitope is intracellular and MCM3 has no transmembrane segment, use a validated permeabilisation step suitable for nuclear staining; optimise it for the IF antibody and specimen (UniProt P25205 topology and localisation; standard IF practice).

How do I separate MCM3 nuclear signal from chromogenic background?

Compare test sections with a no primary control and an appropriate positive control under the same DAB development conditions (standard IHC practice). In the PA1651 example, sections received 10% goat serum block, 2 μg/ml primary antibody overnight at 4°C, and a peroxidase conjugated secondary for 30 minutes at 37°C (datasheet PA1651). If the no primary control develops colour, check endogenous peroxidase blocking and detection reagents before changing MCM3 retrieval (standard IHC practice). If background appears only with primary antibody, titrate it downward and improve washing while monitoring expected nuclear staining in the positive control (UniProt P25205 nucleus; standard IHC practice).

How should I quantify MCM3 staining across differently cellular tissues? ⚠ ANSWER MARKED FOR VERIFICATION

Define positive nuclear DAB against a fixed threshold established with controls, then report the percentage of positive nuclei among evaluable cells in each chosen compartment (UniProt P25205 nucleus; standard IHC practice). An H-score can additionally capture intensity, while positive nuclei per mm² describes spatial density; state which metric answers the study question (standard IHC practice). Normalise counts to the total eligible nuclei or sampled tissue area, and exclude folds, necrosis and poorly counterstained regions by the same rules across slides (standard IHC practice). Report the sampled regions because MCM3 expression is nuclear in proliferating cells and cell composition may vary (HPA tissue IHC).

What findings make an apparent MCM3 IHC positive result suspect?

A credible result shows staining in intact nuclei and a plausible cell distribution, with high staining reported in bone marrow hematopoietic cells and placental cytotrophoblasts (UniProt P25205 nucleus; HPA tissue IHC). Strong colour confined to section edges, necrotic regions or the no primary control suggests staining artefact or detection background (standard IHC practice). Predominantly cytoplasmic DAB warrants reassessment because the expected localisation is nuclear or nucleoplasmic (UniProt P25205 subcellular annotation; HPA subcellular). Interpret a negative region cautiously: the tissue IHC profile has Supported reliability with medium consistency between staining and RNA expression, and MCM3 expression varies across cell populations (HPA tissue IHC).

Boster reagents

Best MCM3 / DNA replication licensing factor MCM3 IHC Antibodies

Catalog-listed anti-MCM3 antibodies cover IHC and IF/ICC in human, mouse, and rat (catalog: applications and reactivity). PA1651 has IHC images from human and rat tissues and IF/ICC data from HeLa cells (PA1651 captions).

Real IHC data

Anti-MCM3 Antibody ®

Cat # PA1651

View product →

PA1651 has IHC images from paraffin sections of human cervical cancer, human breast cancer, and rat spleen, plus an IF/ICC image from HeLa cells (PA1651 image captions). M02580 is listed for IHC and IF/ICC in human, mouse, and rat, but has no supplied specimen images (catalog: M02580 applications, reactivity, image alts).

Which to pick: Choose PA1651 for paraffin-section tissue IHC: its own captions document human and rat sections; the fixative is unreported (PA1651 IHC captions). For IF/ICC, PA1651 has a HeLa-cell image, while M02580 lists IF/ICC without a supplied image (PA1651 IF caption; catalog: M02580 applications and image alts). For cross-species planning, both list human, mouse, and rat reactivity; PA1651 shows human and rat IHC, while M02580 is a rabbit monoclonal without supplied IHC images (catalog: reactivity and M02580 clone; PA1651 IHC captions).

Each figure is that product's own IHC / IF validation image from its datasheet.

References

UniProt Consortium. UniProt entry P25205 (MCM3_HUMAN, DNA replication licensing factor MCM3).
Human Protein Atlas. MCM3 tissue IHC expression (reliability: Supported).
Human Protein Atlas. MCM3 subcellular location (ICC-IF): Localized to the nucleoplasm..
Human Protein Atlas. MCM3 antibody validation summary (3 antibodies).
Expression of gamma-aminobutyric acid type A receptor subunit π and minichromosome maintenance-3 in breast cancer patients treated with neoadjuvant chemotherapy: a target molecule or a proliferation marker?. Revista da Associacao Medica Brasileira (1992) 2025 — PMC12534050.
High MCM3 expression is an independent biomarker of poor prognosis and correlates with reduced RBM3 expression in a prospective cohort of malignant melanoma. Diagnostic pathology 2012 — PMC3433373.
MCM3 is a novel proliferation marker associated with longer survival for patients with tubo-ovarian high-grade serous carcinoma. Virchows Archiv : an international journal of pathology 2022 — PMC9035053.
Expression, potential biological behaviour and clinical significance of MCM3 in pancreatic adenocarcinoma: a comprehensive study integrating high throughput sequencing, CRISPR screening and in-house immunohistochemistry. Annals of medicine 2024 — PMC11421141.
PubMed PMID:8265339 — UniProt-cited evidence.
PubMed PMID:7758114 — UniProt-cited evidence.
PubMed PMID:14702039 — UniProt-cited evidence.