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Modeling ATM mutant proteins from missense changes confirms retained kinase activity
Author(s) -
Barone Giancarlo,
Groom Alix,
Reiman Anne,
Srinivasan Venkataramanan,
Byrd Philip J.,
Taylor A. Malcolm R.
Publication year - 2009
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.21034
Subject(s) - biology , dna pkcs , mutant , ataxia telangiectasia , kinase , protein kinase a , map2k7 , microbiology and biotechnology , cyclin dependent kinase 2 , mutant protein , biochemistry , dna damage , dna , gene
Ataxia‐telangiectasia mutated ( ATM ) is the gene mutated in the cancer‐predisposing disorder ataxia‐telangiectasia (A‐T). We modeled ATM sequence variants identified in UK A‐T patients to determine the stability and kinase activity of the resulting proteins as well as the distribution of these mutations across the coding region. Of 20 missense changes modeled, 10 proteins showed ATM kinase activity and 10 showed none. In the majority of cases the mutant ATM protein was unstable, although this was variable. Reduction in ATM kinase activity can result either from the presence of low levels of unstable mutant protein with relatively normal specific kinase activity or from stable mutant protein with deficient ATM kinase activation. Indeed, ATM mutant proteins without kinase activity toward downstream targets were still able to autophosphorylate on serine 1981, although in a much less efficient manner, suggesting that this was not sufficient for ATM activation. In terms of function, green fluorescent protein (GFP)‐tagged kinase inactive ATM proteins could form ionizing radiation (IR)‐induced foci (IRIF), at least temporarily, which colocalized with the DNA double‐strand break (DSB) marker γH2AX. Consistent with this, both kinase active and inactive mutant ATM proteins were able to interfere with phosphorylation of targets by endogenous ATM. Since the majority of missense mutations occurred C‐terminal to aa1966, including all 10 mutations with absence of kinase activity, the implication was that mutations N‐terminal to this, with exceptions, are less likely to result in loss of kinase activity and therefore, are less likely to be identified in A‐T patients. Hum Mutat 30:1–9, 2009. © 2009 Wiley‐Liss, Inc.