Modeling ATM Mutant Proteins From Missense Changes Confirms Retained Kinase Activity
Modeling ATM Mutant Proteins From Missense Changes Confirms Retained Kinase Activity
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DOI：
10.1002/humu.21034
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发表时间：
2009-08-01
期刊：
影响因子：
3.9
通讯作者：
Taylor, A. Malcolm R.
中科院分区：
文献类型：
--
作者：
Barone, Giancarlo;Groom, Alix;Taylor, A. Malcolm R.
共济失调毛细血管扩张突变（ATM）是在癌症易感性疾病共济失调毛细血管扩张（A-T）中发生突变的基因。我们对在英国A-T患者中鉴定的ATM序列变体进行建模，以确定所得蛋白质的稳定性和激酶活性以及这些突变在编码区中的分布。在20个错义变化模型中，10个蛋白质显示ATM激酶活性，10个蛋白质无活性。在大多数情况下，突变ATM蛋白是不稳定的，虽然这是可变的。ATM激酶活性的降低可由低水平的具有相对正常的特异性激酶活性的不稳定突变蛋白的存在或由具有缺陷的ATM激酶活化的稳定突变蛋白引起。事实上，对下游靶点没有激酶活性的ATM突变蛋白仍然能够在丝氨酸1981上自磷酸化，尽管以低得多的效率方式，这表明这不足以激活ATM。在功能方面，绿色荧光蛋白（GFP）标记的激酶失活ATM蛋白可以形成电离辐射（IR）诱导的病灶（IRIF），至少是暂时的，与DNA双链断裂（DSB）标记γ H2 AX共定位。与此一致，激酶活性和失活突变ATM蛋白能够干扰内源性ATM的靶点磷酸化。由于大多数错义突变发生在aa 1966的C-末端，包括所有10个缺乏激酶活性的突变，这意味着除了例外，N-末端突变不太可能导致激酶活性丧失，因此不太可能在A-T患者中鉴定出。《Mutat》30，1222-1230，2009年。(C)2009威利-利斯公司
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 gamma H2AX. 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, 1222-1230, 2009. (C) 2009 Wiley-Liss, Inc.