Cytoplasmic irradiation induces mitochondrial-dependent 53BP1 protein relocalization in irradiated and bystander cells

TY - JOUR

T1 - Cytoplasmic irradiation induces mitochondrial-dependent 53BP1 protein relocalization in irradiated and bystander cells

AU - Tartier, Laurence

AU - Gilchrist, Stuart

AU - Burdak-Rothkamm, Susanne

AU - Folkard, Melvyn

AU - Prise, Kevin M

PY - 2007/6/15

Y1 - 2007/6/15

N2 - The accepted paradigm for radiation effects is that direct DNA damage via energy deposition is required to trigger the downstream biological consequences. The radiation-induced bystander effect is the ability of directly irradiated cells to interact with their nonirradiated neighbors, which can then show responses similar to those of the targeted cells. p53 binding protein 1 (53BP1) forms foci at DNA double-strand break sites and is an important sensor of DNA damage. This study used an ionizing radiation microbeam approach that allowed us to irradiate specifically the nucleus or cytoplasm of a cell and quantify response in irradiated and bystander cells by studying ionizing radiation-induced foci (IRIF) formation of 53BP1 protein. Our results show that targeting only the cytoplasm of a cell is capable of eliciting 53BP1 foci in both hit and bystander cells, independently of the dose or the number of cells targeted. Therefore, direct DNA damage is not required to trigger 53BP1 IRIF. The use of common reactive oxygen species and reactive nitrogen species (RNS) inhibitors prevent the formation of 53BP1 foci in hit and bystander cells. Treatment with filipin to disrupt membrane-dependent signaling does not prevent the cytoplasmic irradiation-induced 53BP1 foci in the irradiated cells, but it does prevent signaling to bystander cells. Active mitochondrial function is required for these responses because pseudo-rho(0) cells, which lack mitochondrial DNA, could not produce a bystander signal, although they could respond to a signal from normal rho+ cells.

AB - The accepted paradigm for radiation effects is that direct DNA damage via energy deposition is required to trigger the downstream biological consequences. The radiation-induced bystander effect is the ability of directly irradiated cells to interact with their nonirradiated neighbors, which can then show responses similar to those of the targeted cells. p53 binding protein 1 (53BP1) forms foci at DNA double-strand break sites and is an important sensor of DNA damage. This study used an ionizing radiation microbeam approach that allowed us to irradiate specifically the nucleus or cytoplasm of a cell and quantify response in irradiated and bystander cells by studying ionizing radiation-induced foci (IRIF) formation of 53BP1 protein. Our results show that targeting only the cytoplasm of a cell is capable of eliciting 53BP1 foci in both hit and bystander cells, independently of the dose or the number of cells targeted. Therefore, direct DNA damage is not required to trigger 53BP1 IRIF. The use of common reactive oxygen species and reactive nitrogen species (RNS) inhibitors prevent the formation of 53BP1 foci in hit and bystander cells. Treatment with filipin to disrupt membrane-dependent signaling does not prevent the cytoplasmic irradiation-induced 53BP1 foci in the irradiated cells, but it does prevent signaling to bystander cells. Active mitochondrial function is required for these responses because pseudo-rho(0) cells, which lack mitochondrial DNA, could not produce a bystander signal, although they could respond to a signal from normal rho+ cells.

KW - Cell Nucleus/radiation effects

KW - Cytoplasm/radiation effects

KW - DNA Damage/radiation effects

KW - DNA, Mitochondrial/radiation effects

KW - Fluorescent Antibody Technique

KW - HeLa Cells

KW - Humans

KW - Intracellular Signaling Peptides and Proteins/metabolism

KW - Mitochondria/metabolism

KW - Polymerase Chain Reaction

KW - Protein Transport/radiation effects

KW - Radiation, Ionizing

KW - Tumor Suppressor p53-Binding Protein 1

U2 - 10.1158/0008-5472.CAN-07-0188

DO - 10.1158/0008-5472.CAN-07-0188

M3 - SCORING: Journal article

C2 - 17575156

VL - 67

SP - 5872

EP - 5879

JO - CANCER RES

JF - CANCER RES

SN - 0008-5472

IS - 12

ER -