Phospho-Histone H3 (Thr3) Antibody

Definition and Mechanism

Phosphorylation of histone H3 at Thr3 is catalyzed by the kinase haspin, which is active during mitosis . This modification recruits Aurora kinase B (AURKB) and the chromosomal passenger complex (CPC) to kinetochores, ensuring proper chromosome alignment during cell division . The antibody specifically binds to the phosphorylated Thr3 residue, enabling detection via techniques like immunohistochemistry (IHC), Western blotting, and proximity-based assays.

HTRF (Homogeneous Time-Resolved Fluorescence) Assay

The HTRF-based detection kit (e.g., Revvity HTRF Human & Mouse Phospho-Histone H3 Thr3 Kit) uses two labeled antibodies: one donor fluorophore-targeting phosphorylated Thr3 and an acceptor fluorophore-binding histone H3 independently of phosphorylation. This no-wash, plate-based assay achieves 16-fold higher sensitivity than Western blotting and requires only 16 µL of lysate per sample .

• Cell culture: HeLa or NIH-3T3 cells at 80% confluence.

• Stimulation: Treat with Calyculin A for 30 min.

• Lysis: 50 µL lysis buffer for 30 min.

• Detection: Transfer 16 µL lysate to a 384-well plate, add 4 µL detection reagents, and measure fluorescence after 2h incubation.

Western Blotting

Western blotting remains a standard method for validating phosphorylation. The antibody (e.g., Cell Signaling Technology, Cat. No. 210838) requires denaturing gel electrophoresis and immunoblotting with enhanced chemiluminescence (ECL) detection .

Role of Haspin Kinase

Haspin phosphorylates Thr3 in mitotic cells, with overexpression leading to enhanced chromosome alignment and RNAi-mediated depletion causing mitotic defects . In vitro assays confirm that recombinant haspin kinase specifically phosphorylates Thr3 in histone H3 .

Clinical Relevance

Phospho-Histone H3 (Thr3) immunostaining correlates with tumor mitotic index, serving as a prognostic marker in cancers like breast melanoma and meningiomas . Studies using this antibody have also identified PP1/Repo-Man phosphatase as a Thr3 dephosphorylase, critical for resetting chromatin during mitotic exit .

Experimental Validation

Applications in Research

• Mitotic studies: Tracking Aurora kinase recruitment to kinetochores .

• Cancer research: Assessing mitotic index for tumor grading .

• Epigenetic studies: Investigating Thr3 phosphorylation in gene regulation .

Challenges and Considerations

• Cross-reactivity: Methylation of Arg2 reduces antibody binding .

• Sample preparation: Requires optimized lysis conditions to preserve phosphorylation .

• Species compatibility: Limited to human and mouse histone H3 .

This antibody remains a cornerstone in mitosis and chromatin research, offering insights into cellular division and disease mechanisms. Its integration into high-throughput assays like HTRF has enhanced scalability, while its specificity ensures reliable data across diverse experimental systems.