title: ATM is down-regulated by N-Myc-regulated microRNA-421.
abstract: Ataxia-telangiectasia mutated (ATM) is a high molecular weight protein serine/threonine kinase that plays a central role in the maintenance of genomic integrity by activating cell cycle checkpoints and promoting repair of DNA double-strand breaks. Little is known about the regulatory mechanisms for ATM expression itself. MicroRNAs are naturally existing regulators that modulate gene expression in a sequence-specific manner. Here, we show that a human microRNA, miR-421, suppresses ATM expression by targeting the 3'-untranslated region (3'UTR) of ATM transcripts. Ectopic expression of miR-421 resulted in S-phase cell cycle checkpoint changes and an increased sensitivity to ionizing radiation, creating a cellular phenotype similar to that of cells derived from ataxia-telangiectasia (A-T) patients. Blocking the interaction between miR-421 and ATM 3'UTR with an antisense morpholino oligonucleotide rescued the defective phenotype caused by miR-421 overexpression, indicating that ATM mediates the effect of miR-421 on cell cycle checkpoint and radiosensitivity. Overexpression of the N-Myc transcription factor, an oncogene frequently amplified in neuroblastoma, induced miR-421 expression, which, in turn, down-regulated ATM expression, establishing a linear signaling pathway that may contribute to N-Myc-induced tumorigenesis in neuroblastoma. Taken together, our findings implicate a previously undescribed regulatory mechanism for ATM expression and ATM-dependent DNA damage response and provide several potential targets for treating neuroblastoma and perhaps A-T.
authors.affiliation: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at the University of California, Los Angeles, CA 90095, USA. hhu@mednet.ucla.edu
authors.forename: Hailiang
authors.initials: H
authors.lastname: Hu
authors.forename: Liutao
authors.initials: L
authors.lastname: Du
authors.forename: Gindy
authors.initials: G
authors.lastname: Nagabayashi
authors.forename: Robert C
authors.initials: RC
authors.lastname: Seeger
authors.forename: Richard A
authors.initials: RA
authors.lastname: Gatti
mesh_terms: D020413:3' Untranslated Regions; D064007:Ataxia Telangiectasia Mutated Proteins; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000235:genetics*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000528:radiation effects; D015398:Signal Transduction; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020413:3' Untranslated Regions; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C547665:MIRN421 microRNA, human; D035683:MicroRNAs; D016271:Proto-Oncogene Proteins c-myc; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases