Involvement of H4(D10S170) protein in ATM-dependent response to DNA damage.
H4(D10S170) gene has been identified upon its frequent rearrangement with RET in papillary thyroid tumours (RET/PTC1). The kinase ataxia telangectasia mutated (ATM) phosphorylates a limited number of downstream protein targets in response to DNA damage. We investigated the potential role of H4(D10S170) in DNA damage signaling pathways. We found that in cells treated with etoposide or ionizing radiation (IR), H4(D10S170) underwent ATM-mediated phosphorylation at Thr 434, stabilizing nuclear H4. In ataxia telangectasia cells (A-T), endogenous H4(D10S170) was localized to cytoplasm and was excluded from the nucleus. Moreover, H4(D10S170) was not phosphorylated in ATM-deficient lymphoblasts after ionizing irradiation. Inhibition of ATM kinase interfered with H4(D10S170) apoptotic activity, and expression of H4 with threonine 434 mutated in Alanine, H4(T434A), protected the cells from genotoxic stress-induced apoptosis. Most importantly, after exposure to IR we found that silencing of H4(D10S170) in mammalian cells increased cell survival, as shown by clonogenic assay, allows for DNA synthesis as evaluated by bromodeoxyuridine incorporation and permits cells to progress into mitosis as demonstrated by phosphorylation on Histone H3. Our results suggest that H4(D10S170) is involved in cellular response to DNA damage ATM-mediated, and that the impairment of H4(D10S170) gene function might have a role in thyroid carcinogenesis.
Merolla
F
F
Dipartimento di Biologia e Patologia Cellulare e Molecolare, University 'Federico II', Naples, Italy.
Pentimalli
F
F
Pacelli
R
R
Vecchio
G
G
Fusco
A
A
Grieco
M
M
Celetti
A
A
D000595:Amino Acid Sequence; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000502:physiology*; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004249:DNA Damage / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000502:physiology*; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D013964:Thyroid Neoplasms / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000502:physiology*
C088832:CCDC6 protein, human; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases