Open AccessDNA Damage-Induced Cell Cycle Regulation and Function of Novel Chk2 Phosphoresidues
Author(s) -
Giacomo Buscemi,
Luigi Carlessi,
Laura Zannini,
Sofia Lisanti,
Enrico Fontanella,
Silvana Canevari,
Domenico Delia
Publication year - 2006
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.00534-06
Subject(s) - checkpoint kinase 2 , phosphorylation , dna damage , autophosphorylation , biology , cell cycle checkpoint , cell cycle , dna repair , chek1 , kinase , microbiology and biotechnology , dna , apoptosis , biochemistry , protein kinase a
Chk2 kinase is activated by DNA damage to regulate cell cycle arrest, DNArepair, and apoptosis. Phosphorylation of Chk2 in vivo byataxia telangiectasia-mutated (ATM) on threonine 68 (T68) initiates aphosphorylation cascade that promotes the full activity of Chk2. Weidentified three serine residues (S19, S33, and S35) on Chk2 thatbecame phosphorylated in vivo rapidly and exclusively in response toionizing radiation (IR)-induced DNA double-strand breaks in an ATM- andNbs1-dependent but ataxia telangiectasia- and Rad3-related-independentmanner. Phosphorylation of these residues, restricted to theG1 phase of the cell cycle, was induced by a higher dose ofIR (>1 Gy) than that required for phosphorylation of T68 (0.25Gy) and declined by 45 to 90 min, concomitant with a rise in Chk2autophosphorylation. Compared to the wild-type form, Chk2 with alaninesubstitutions at S19, S33, and S35 (Chk2S3A ) showed impaireddimerization, defective auto- andtrans -phosphorylationactivities, and reduced ability to promote degradation of Hdmx, aphosphorylation target of Chk2 and regulator of p53 activity.Besides, Chk2S3A failed to inhibit cell growth and, inresponse to IR, to arrest G1 /S progression. These findingsunderscore the critical roles of S19, S33, and S35 and argue that thesephosphoresidues may serve to fine-tune the ATM-dependent response ofChk2 to increasing amounts of DNA damage.