Ionizing radiation induces a dramatic persistence of p53 protein accumulation and DNA damage signaling in mutant p53 zebrafish.
Mutant p53 proteins accumulate to high levels in human tumors and in preneoplastic lesions in the skin and fallopian tube. However examination of tissues from mice and fish that are homozygous for mutant p53 surprisingly showed that the protein was present only at low levels except in the tumors that arose in these animals. The mutant protein did accumulate, however, following treatment with ionizing radiation in the same tissues in which the wild-type protein is induced. Here we study in detail the accumulation of mutant and wild-type p53 proteins following ionizing radiation in zebrafish embryos. We found that the mutant protein was induced by lower levels of radiation and reached higher levels than the wild-type protein. Morpholino knockdown of the zebrafish homologs of Mdm2 and Mdm4 caused dramatic accumulation of mutant p53 protein. The most remarkable results were observed by examining p53 protein levels over an extended time course. Mutant p53 protein increased and persisted for days after irradiation and this was accompanied by persistent elevation of phosphorylated H2AX (γH2AX), implying that the resolution of DNA damage signaling in these embryos is severely compromised by mutations in p53. Thus mutation in p53 results in an exaggerated and persistent damage response, which could in turn drive the process of cancer development as high levels of mutant p53 can act as an oncoprotein to drive invasion and metastasis.
p53 Laboratory, Biomedical Science Institutes, Singapore.
L
L
Guo
H P
HP
Liew
S
S
Camus
A M
AM
Goh
L L
LL
Chee
D P
DP
Lunny
E B
EB
Lane
D P
DP
Lane
D000818:Animals; D015153:Blotting, Western; D004249:DNA Damage; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism / Q000528:radiation effects; D005134:Eye Neoplasms / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006657:Histones / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D007150:Immunohistochemistry; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000528:radiation effects; D009381:Neoplasms, Radiation-Induced / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D051736:Proto-Oncogene Proteins c-mdm2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011839:Radiation, Ionizing; D015398:Signal Transduction / Q000528:radiation effects*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
D006657:Histones; D007093:Imidazoles; C584465:Mdm4 protein, zebrafish; D050505:Mutant Proteins; D010750:Phosphoproteins; D010879:Piperazines; D016159:Tumor Suppressor Protein p53; D029961:Zebrafish Proteins; C482205:nutlin 3; D051736:Proto-Oncogene Proteins c-mdm2