Upregulated ATM gene expression and activated DNA crosslink-induced damage response checkpoint in Fanconi anemia: implications for carcinogenesis.

Abstract

Fanconi anemia (FA) predisposes to hematopoietic failure, birth defects, leukemia, and squamous cell carcinoma of the head and neck (HNSCC) and cervix. The FA/BRCA pathway includes 8 members of a core complex and 5 downstream gene products closely linked with BRCA1 or BRCA2. Precancerous lesions are believed to trigger the DNA damage response (DDR), and we focused on the DDR in FA and its putative role as a checkpoint barrier to cancer. In primary fibroblasts with mutations in the core complex FANCA protein, we discovered that basal expression and phosphorylation of ATM (ataxia telangiectasia mutated) and p53 induced by irradiation (IR) or mitomycin C (MMC) were upregulated. This heightened response appeared to be due to increased basal levels of ATM in cultured FANCA-mutant cells, highlighting the new observation that ATM can be regulated at the transcriptional level in addition to its well-established activation by autophosphorylation. Functional analysis of this response using gamma-H2AX foci as markers of DNA double-stranded breaks (DSBs) demonstrated abnormal persistence of only MMC- and not IR-induced foci. Thus, we describe a processing defect that leads to general DDR upregulation but specific persistence of DNA crosslinker-induced damage response foci. Underscoring the significance of these findings, we found resistance to DNA crosslinker-induced cell cycle arrest and apoptosis in a TP53-mutant, patient-derived HNSCC cell line, whereas a lymphoblastoid cell line derived from this same individual was not mutated at TP53 and retained DNA crosslinker sensitivity. Our results suggest that cancer in FA may arise from selection for cells that escape from a chronically activated DDR checkpoint.

• Authors: Kazuhiko Yamamoto, Abdallah Nihrane, Jason Aglipay, Juan Sironi, Steven Arkin, Jeffrey M Lipton, Toru Ouchi, Johnson M Liu
• Journal: Molecular medicine (Cambridge, Mass.) (Mol Med) 2008 Mar-Apr Vol. 14 Issue 3-4 Pg. 167-74 ISSN: 1076-1551 [Print] England
• PMID: 18224251 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Cell Cycle Proteins
• DNA-Binding Proteins
• FANCA protein, human
• Fanconi Anemia Complementation Group A Protein
• Tumor Suppressor Protein p53
• Tumor Suppressor Proteins
• ATM protein, human
• Ataxia Telangiectasia Mutated Proteins
• Protein Serine-Threonine Kinases

Topics

• Adult
• Animals
• Apoptosis (physiology)
• Ataxia Telangiectasia Mutated Proteins
• Cell Cycle (physiology)
• Cell Cycle Proteins (genetics, metabolism)
• Cells, Cultured
• DNA Damage
• DNA Repair
• DNA-Binding Proteins (genetics, metabolism)
• Fanconi Anemia (complications, genetics, metabolism)
• Fanconi Anemia Complementation Group A Protein (genetics, metabolism)
• Fibroblasts (cytology, physiology)
• Gene Expression Regulation
• Humans
• Neoplasms (etiology, metabolism)
• Protein Serine-Threonine Kinases (genetics, metabolism)
• RNA Interference
• Tumor Suppressor Protein p53 (genetics, metabolism)
• Tumor Suppressor Proteins (genetics, metabolism)
• Up-Regulation