The mammalian histone H2AX protein functions as a dosage-dependent genomic caretaker and tumor suppressor. Phosphorylation of H2AX to form γ-H2AX in chromatin around DNA double strand breaks (DSBs) is an early event following induction of these hazardous lesions. For a decade, mechanisms that regulate H2AX phosphorylation have been investigated mainly through two-dimensional immunofluorescence (IF). We recently used chromatin immunoprecipitation (ChIP) to measure γ-H2AX densities along chromosomal DNA strands broken in G 1 phase mouse lymphocytes. Our experiments revealed that (1) γ-H2AX densities in nucleosomes form at high levels near DSBs and at diminishing levels farther and farther away from DNA ends, and (2) ATM regulates H2AX phosphorylation through both MDC1-dependent and MDC1-independent means. Neither of these mechanisms were discovered by previous IF studies due to the inherent limitations of light microscopy. Here, we compare data obtained from parallel γ-H2AX ChIP and three-dimensional IF analyses and discuss the impact of our findings upon molecular mechanisms that regulate H2AX phosphorylation in chromatin around DNA breakage sites. © 2009 Landes Bioscience.
CITATION STYLE
Savic, V., Sanborn, K. B., Orange, J. S., & Bassing, C. H. (2009, October 15). Chipping away at γ-H2AX foci. Cell Cycle. Taylor and Francis Inc. https://doi.org/10.4161/cc.8.20.9719
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