ATM activity contributes to the tumor-suppressing functions of p14ARF.
P14/p19ARF (ARF) plays a major role in the activation of p53 by oncogenic signals. The biochemical basis of this has not been fully elucidated. We report here that forced expression of p14ARF enhances phosphorylation of p53 serine 15 (p53S15) in NIH3T3, IMR90 and MCF7 cells. Ectopic expression of the oncogenes c-myc, E2F1 and E1A, all of which activate p53 at least partially via ARF, lead to p53S15 phosphorylation in IMR90 cells. In addition, ectopic expression of p53 also results in p53S15 phosphorylation, suggesting that this is a common event in the ARF-p53 tumor suppression system. Furthermore, p53-, p14ARF-, c-myc- and E2F1-, but not E1A-, induced p53S15 phosphorylation was substantially reduced in AT fibroblasts (GM05823). Downregulation of ATM in MCF7 cells using RNA interference (RNAi) technology significantly attenuated p14ARF- and p53-induced phosphorylation of p53S15. Ectopically expressed ARF in NIH3T3 cells induced ATM nuclear foci and activated ATM kinase. Functionally, ectopic expression of p14ARF and c-myc inhibited the proliferation of IMR90 but not ATM null GM05823 cells, and p14ARF-induced inhibition of MCF7 cell proliferation was significantly attenuated by downregulation of ATM by RNAi. Taken together, these data show a functional role for ATM in ARF-mediated tumor suppression.
Li
Yanxia
Y
Division of Nephrology, Department of Medicine, McMaster University, Hamilton, ON, Canada.
Wu
Dongcheng
D
Chen
Biao
B
Ingram
Alistair
A
He
Lizhi
L
Liu
Lieqi
L
Zhu
Dahai
D
Kapoor
Anil
A
Tang
Damu
D
D016475:3T3 Cells; D000818:Animals; D001260:Ataxia Telangiectasia / Q000235:genetics / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000235:genetics; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins; D016259:Genes, myc / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016372:RNA, Antisense / Q000235:genetics; D034741:RNA, Small Interfering; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016372:RNA, Antisense; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases