Role of a BRCT domain in the interaction of DNA ligase III-alpha with the DNA repair protein XRCC1.
Role of a BRCT domain in the interaction of DNA ligase III-alpha with the DNA repair protein XRCC1.
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发表时间：
1998
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通讯作者：
R. Taylor;B. Wickstead;S. Cronin;K. Caldecott
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作者：
R. Taylor;B. Wickstead;S. Cronin;K. Caldecott
BRCT结构域(BRCA1羧基末端)是一个功能未知的蛋白质基序，由大约100个氨基酸组成，位于5个保守的A-E块中。BRCT结构域存在于肿瘤抑制蛋白BRCA1[1-3]中，该结构域存在于40多种其他蛋白质中，定义了一个超家族，包括DNA连接酶III-α和基本的人类DNA修复蛋白XRCC1。DNA连接酶III-α和XRCC1通过它们的羧基末端相互作用，靠近或在包含BRCT结构域的区域内[4]。为了研究XRCC1的羧基末端BRCT结构域(记为BRCT II)的主要作用是否是介导与DNA连接酶III-α的相互作用，我们确定了该结构域中相互作用所需和充分的区域。其中保守的D-块色氨酸被点突变破坏的XRCC1蛋白保留了与DNA连接酶III-α相互作用的能力，因此这种色氨酸必须介导一个不同的、尽管保守的角色。弱保守C区突变的XRCC1失去了与DNA连接酶III-α相互作用的能力。此外，跨越BRCT II C-块的20个氨基酸赋予一个无关的多肽完全的DNA连接酶III-α结合活性。缺失这个20聚体的XRCC1蛋白不能在转基因的啮齿动物细胞中维持DNA连接酶III-α的正常水平，这是一种与缺陷修复相关的表型[5]。综上所述，这些数据表明，BRCT结构域可以调节生物上重要的蛋白质-蛋白质相互作用，并支持额外角色的存在。
The BRCT domain (for BRCA1 carboxyl terminus) is a protein motif of unknown function, comprising approximately 100 amino acids in five conserved blocks denoted A-E. BRCT domains are present in the tumour suppressor protein BRCA1 [1-3], and the domain is found in over 40 other proteins, defining a superfamily that includes DNA ligase III-alpha and the essential human DNA repair protein XRCC1. DNA ligase III-alpha and XRCC1 interact via their carboxyl termini, close to or within regions that contain a BRCT domain [4]. To examine whether the primary role of the carboxy-terminal BRCT domain of XRCC1 (denoted BRCT II) is to mediate the interaction with DNA ligase III-alpha, we identified the regions of the domain that are required and sufficient for the interaction. An XRCC1 protein in which the conserved D-block tryptophan was disrupted by point mutation retained the ability to interact with DNA ligase III-alpha, so this tryptophan must mediate a different, although conserved, role. XRCC1 in which the weakly conserved C-block was mutated lost the ability to interact with DNA ligase III-alpha. Moreover, 20 amino acids spanning the C-block of BRCT II conferred full DNA ligase III-alpha binding activity upon an unrelated polypeptide. An XRCC1 protein in which this 20mer was deleted could not maintain normal levels of DNA ligase III-alpha in transfected rodent cells, a phenotype associated with defective repair [5]. In summary, these data demonstrate that a BRCT domain can mediate a biologically important protein-protein interaction, and support the existence of additional roles.