Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P16104 (H2AX)
 3,930 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

BRIT1 [BRCT-repeat inhibitor of hTERT expression], a repressor of human telomerase function, is implicated in cellular immortalization. Here, we find that BRIT1 acts as a regulator of both the intra-S and G2/M checkpoints. When BRIT1 expression is depleted, cells lose the ionizing radiation (IR)-induced cell cycle arrest and become IR sensitive. BRIT1 is a chromatin-associated protein that forms irradiation-induced nuclear foci that colocalize with gamma-H2AX foci. BRIT1 is also required for the expression of both BRCA1 and the checkpoint kinase Chk1 and phosphorylation of Nbs1. Thus, the checkpoint defects in the absence of BRIT1 are likely to result from its regulation of Nbs1, BRCA1, and Chk1. BRIT1 is identical to the recently discovered MCPH1 gene, found mutant in patients with primary microcephaly. The ataxia telangiectasia mutated-Rad3 related (ATR)-Chk1 pathway is defective in Seckel syndrome, another microcephaly disorder. We propose that the microcephaly observed in patients with MCPH1 deficiencies is due to disruption of the ATR-BRCA1-Chk1 signaling pathway that is also disrupted in Seckel syndrome patients.
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PMID:BRIT1/MCPH1 is a DNA damage responsive protein that regulates the Brca1-Chk1 pathway, implicating checkpoint dysfunction in microcephaly. 1621 32

It has been suggested that phosphorylation of the histone variant H2AX after ultraviolet light (UV) irradiation is triggered by DNA double-strand breaks induced as replication forks collide with UV-induced bulky lesions. More recently, it has been shown that UV-induced H2AX phosphorylation can also occur outside of S-phase, but the mechanism for this replication-independent induction is not well understood. In this study, we show that H2AX phosphorylation after UV irradiation is triggered by DNA repair intermediates and is induced in all phases of the cell cycle. Accumulation of DNA repair intermediates by inhibition of DNA repair synthesis resulted in a marked increase of H2AX phosphorylation in repair proficient but not repair-deficient xeroderma pigmentosum-A cells. Using chemical inhibitors of the PI(3)-like kinase family of protein kinases as well as ataxia telangiectasia mutated and Rad-3 related (ATR)-deficient Seckel syndrome cells and ataxia telangiectasia mutated-deficient ataxia telangiectasia cells, we show that the H2AX phosphorylation induced by accumulation of repair intermediates is mediated primarily by the ATR kinase. We suggest a model for UV light-induced phosphorylation of H2AX where in addition to replication blockage, DNA repair intermediates trigger H2AX phosphorylation via the ATR kinase.
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PMID:H2AX phosphorylation after UV irradiation is triggered by DNA repair intermediates and is mediated by the ATR kinase. 1761 56

Ataxia telangiectasia and Rad3-related (ATR) is a phosphoinositol-3-kinase like kinase (PIKK) that initiates a signal transduction response to replication fork stalling. Defects in ATR signalling have been reported in several disorders characterized by microcephaly and growth delay. Here, we gain insight into factors influencing the ATR signalling pathway and consider how they can be exploited for diagnostic purposes. Activation of ATR at stalled replication forks leads to intra-S and G2/M phase checkpoint arrest. ATR also phosphorylates gamma-H2AX at single-stranded (ss) DNA regions generated during nucleotide excision repair (NER) in non-replicating cells, but the critical analysis of any functional consequence has not been reported. Here, we show that UV irradiation of G2 phase cells causes ATR-dependent but replication-independent G2/M checkpoint arrest. This process requires the Nbs1 N-terminus encompassing the FHA and BRCT domains but not the Nbs1 C-terminus in contrast to ATM-dependent activation of G2/M arrest in response to ionizing radiation. Thus, Nbs1 has a function in ATR signalling in a manner distinct to any role at stalled replication forks. Replication-independent ATR signalling also requires the mediator proteins, 53BP1 and MDC1, providing direct evidence for their role in ATR signalling, but not H2AX. Finally, the process is activated in Cockayne's syndrome but not Xeroderma pigmentosum group A cells providing evidence that ssDNA regions generated during NER are the ATR-pathway-specific activating lesion. Replication-independent G2/M checkpoint arrest represents a suitable assay to specifically identify patients with defective ATR signalling, including Seckel syndrome, Nijmegen breakage syndrome and MCPH-1-dependent primary microcephaly.
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PMID:Replication independent ATR signalling leads to G2/M arrest requiring Nbs1, 53BP1 and MDC1. 1866 57

Functional impairment of DNA damage response pathways leads to increased genomic instability. Here we describe the centrosomal protein CEP152 as a new regulator of genomic integrity and cellular response to DNA damage. Using homozygosity mapping and exome sequencing, we identified CEP152 mutations in Seckel syndrome and showed that impaired CEP152 function leads to accumulation of genomic defects resulting from replicative stress through enhanced activation of ATM signaling and increased H2AX phosphorylation.
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PMID:CEP152 is a genome maintenance protein disrupted in Seckel syndrome. 2139 65