An anti-sense construct of full-length ATM cDNA imposes a radiosensitive phenotype on normal cells.
The cloning of a full-length cDNA for the gene (ATM) mutated in the human genetic disorder ataxia-telangiectasia (A-T) has been described recently. This cDNA, as well as a fragment representing a functional region from ATM, are capable of rescuing various aspects of the radiosensitive phenotype in A-T cells. We have subcloned full-length ATM cDNA in the opposite orientation in an EBV-based vector under the control of an inducible promoter to determine whether this anti-sense construct might sensitize control lymphoblastoid cells to ionizing radiation. The effectiveness of expression of this construct in control cells was monitored by loss of ATM protein which was evident over a period 6-12 h after induction. Under these conditions radiosensitivity was enhanced approximately threefold in control cells, approaching the degree of radiosensitivity observed in A-T cells. Expression of the anti-sense construct also increased the number of radiation-induced chromosomal breaks and led to the appearance of radioresistant DNA synthesis in these cells. Abrogation of the G1/S checkpoint was evident from the loss of the p53 response and that of its downstream effector, p21/WAF1, post-irradiation. The extent of accumulation of transfected cells in G2/M phase at 24 h post-irradiation was similar to that observed in A-T cells and the induction of stress-activated protein kinase by ionizing radiation was prevented by antisense ATM cDNA expression. These data demonstrate that full-length ATM anti-sense cDNA, by reducing the amount of ATM protein, is effective in imposing a series of known defects characteristic of the A-T phenotype. This inducible system provides an experimental model to further investigate mechanisms underlying radiosensitivity and cell cycle control.
Queensland Cancer Fund Research Laboratories, Brisbane, Australia.
N
N
Zhang
P
P
Chen
M
M
Gatei
S
S
Scott
K K
KK
Khanna
M F
MF
Lavin
D001260:Ataxia Telangiectasia / Q000235:genetics*; D064007:Ataxia Telangiectasia Mutated Proteins; D019256:Cadmium Chloride / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002869:Chromosome Aberrations; D003001:Cloning, Molecular; D004247:DNA / Q000096:biosynthesis; D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D005720:Gamma Rays; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D008214:Lymphocytes; D020928:Mitogen-Activated Protein Kinases; D010641:Phenotype; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*; D011994:Recombinant Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D016373:DNA, Antisense; D004268:DNA-Binding Proteins; D011506:Proteins; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; D004247:DNA; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D019256:Cadmium Chloride