Komine Keigo, Shimodaira Hideki, Takao Masashi, Soeda Hiroshi, Zhang Xiaofei, Takahashi Masanobu, Ishioka Chikashi
Department of Clinical Oncology, Institute of Development, Aging and Cancer, Tohoku University, Aoba-ku, Sendai, Japan.
Department of Clinical Oncology, Tohoku University Hospital, Aoba-ku, Sendai, Japan.
Hum Mutat. 2015 Jul;36(7):704-11. doi: 10.1002/humu.22794.
MUTYH-associated polyposis (MAP) is an adenomatous polyposis transmitted in an autosomal-recessive pattern, involving biallelic inactivation of the MUTYH gene. Loss of a functional MUTYH protein will result in the accumulation of G:T mismatched DNA caused by oxidative damage. Although p.Y179C and p.G396D are the two most prevalent MUTYH variants, more than 200 missense variants have been detected. It is difficult to determine whether these variants are disease-causing mutations or single-nucleotide polymorphisms. To understand the functional consequences of these variants, we generated 47 MUTYH gene variants via site-directed mutagenesis, expressed the encoded proteins in MutY-disrupted Escherichia coli, and assessed their abilities to complement the functional deficiency in the E. coli by monitoring spontaneous mutation rates. Although the majority of variants exhibited intermediate complementation relative to the wild type, some variants severely interfered with this complementation. However, some variants retained functioning similar to the wild type. In silico predictions of functional effects demonstrated a good correlation. Structural prediction of MUTYH based on the MutY protein structure allowed us to interpret effects on the protein stability or catalytic activity. These data will be useful for evaluating the functional consequences of missense MUTYH variants detected in patients with suspected MAP.
MUTYH相关息肉病（MAP）是一种以常染色体隐性模式遗传的腺瘤性息肉病，涉及MUTYH基因的双等位基因失活。功能性MUTYH蛋白的缺失将导致由氧化损伤引起的G:T错配DNA的积累。虽然p.Y179C和p.G396D是两种最常见的MUTYH变体，但已检测到200多种错义变体。很难确定这些变体是致病突变还是单核苷酸多态性。为了了解这些变体的功能后果，我们通过定点诱变产生了47种MUTYH基因变体，在MutY缺失的大肠杆菌中表达编码的蛋白质，并通过监测自发突变率评估它们补充大肠杆菌功能缺陷的能力。虽然大多数变体相对于野生型表现出中等互补性，但一些变体严重干扰了这种互补性。然而，一些变体保留了与野生型相似的功能。对功能效应的计算机预测显示出良好的相关性。基于MutY蛋白结构对MUTYH进行结构预测，使我们能够解释对蛋白质稳定性或催化活性的影响。这些数据将有助于评估在疑似MAP患者中检测到的错义MUTYH变体的功能后果。
