DISCOVERY Antibodies

  • Histone mutations play important roles in DNA organisation

    Histone proteins help compact and organise the DNA of the nucleus, they also play key roles in orchestrating gene expression. The four core histones, H2AH2BH3 and H4 form a complex around which DNA is wound forming the nucleosome. Between the nucleosome is the internucleosomal DNA which is stabilised by the linker histone H1. Modifications of histones can alter the nature of the chromatin and affect its level of compaction, as can histone variants. An example of such a variant is γH2Ax which is associated with DNA double strand breaks, such as during meiosis; for which CRB has raised an antibody.

    Mutations of histone proteins can also have a huge role in how the chromatin is organised and can impact disease. As part of our histone antibody range we have produced two novel mutation specific antibodies able to specifically detect two somatic missense mutant histone H3 (H3.3) proteins. The mutations are at a critical position within the histone tail, glycine 34, and involve amino acid changes to arginine or valine (G34R and G34V). The conversion of glycine to a large side chain containing residue sterically hinders interactions of H3K36-specific methyltransferases such as STED2 with the downstream H3K36 position. This results in the blocking of H3 lysine 36 (H3K36) dimethylation and trimethylation. H3K36me3 is essential for DNA repair, including DNA mismatch repair (MMR) by interacting with mismatch repair (MMR) protein MutSα, and recruiting the MMR machinery to chromatin. MMR corrects errors created during DNA replication and the resulting MMR deficiency leads to genome instability and tumorigenesis.

    Histone H3.3 G34V/R mutations are a hallmark of paediatric diffuse intrinsic pontine gliomas (DIPG), non-brain stem paediatric high grade gliomas (pHGG) and some adult glioblastoma multiforme (GBM) tumours. The anti-H3.3 G34R antibody offered in our DISCOVERY® antibody catalogue has shown high specificity and selectivity to the G34R mutation in paediatric brain tumour sections by immunohistochemistry. This altered histone modification profile promotes a unique gene expression profile that supports enhanced tumour development in vivo.

    Anti-Histone H3.3 G34R mutant-specific antibody can be bought here and anti-Histone H3.3 G34V mutant-specific antibody here as cited in:

    Haque et al., (2017). Acta Neuropathol Commun. 5(1):45. PMID: 28587626

    To read our full case study on the anti-histone H3.3 G34R/V antibodies click here

    References:

    Fang et al., (2018). Cancer-driving H3G34V/R/D mutations block H3K36 methylation and H3K36me3–MutSα interaction. Proc Natl Acad Sci U S A. 115(38): 9598. PMID: 30181289

  • The diverse role of cell cycle regulator, p21

    The multi-functional cyclin-dependent kinase (CDK) inhibitor, p21 plays a diverse role in regulating the DNA damage response, senescence, DNA repair, transcription and apoptosis. p21, also known as p21WAF1/Cip1 or CDKN1A, belongs to the CIP/Kip family of CDK inhibitors.

    In normal cells, p21 functions as a cell cycle inhibitor and anti-proliferative effector. Upon DNA damage and genotoxic stress, the tumour suppressor p53 is activated and induces the expression of p21. p21 can bind to cyclin A/CDK2, E/CDK2, D1/CDK4 and D2/CDK4 complexes and suppress their catalytic activity. This prevents the phosphorylation of Retinoblastoma protein (Rb) and leads to the arrest in G1/S cell cycle progression and G2/M transitions. In addition, p21 also inactivates Rb by mediating its degradation. Studies also show that p21 can mediate cellular senescence via p53-dependent and p53-independent pathways.

    p21 can also acts as either an enhancer or a suppressor of various DNA repair pathways. In DNA damaged cells, p21 is recruited to damaged sites and co-localises with double strand break (DSB) repair proteins to facilitate various repair pathways. p21 has been implicated in nucleotide excision repair (NER), base excision repair (BER) and DNA translesion synthesis (TLS) by disrupting the proliferating cell nuclear antigen (PCNA) interaction with other DNA repair factors and promoting PCNA degradation. PCNA-dependent DNA replication is also inhibited by p21. Another important function of p21 is regulating the transcription of genes involved in various biological process such as cell cycle progression, DNA repair and regulation of apoptosis, such as E2F family, NF-κB, c-myc, STAT and p300/CPB.

    In response to DNA damage and stress signals, p21 has been shown to exert anti-apoptotic activity. The cytoplasmic interaction of p21 with pro-caspase 3 and caspase 2 prevents their activation of apoptosis. Fas-induced apoptosis is also inhibited via p21 interaction with caspase 3 and inhibition of its activity. p21 also forms a complex with stress induced kinases, such as apoptosis signal regulating kinase 1 (ASK1) to inhibit apoptosis. In addition, the phosphorylation of p21 by Akt1/PKB enhances its stability and promotes cell survival.

    Anti-p21 Antibody (crb2005030)

    Read more: Phospho-specific Antibodies: Focus on CDK1

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