The BARD1 C-Terminal Domain Structure and Interactions with Polyadenylation Factor CstF-50

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• 作者：Ross A. Edwards ; Megan S. Lee ; Susan E. Tsutakawa ; R. Scott Williams ; John A. Tainer ; J. N. Mark Glover
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：November 4, 2008
• 年：2008
• 卷：47
• 期：44
• 页码：11446-11456
• 全文大小：401K
• 年卷期：v.47,no.44(November 4, 2008)
• ISSN：1520-4995

文摘

The BARD1 N-terminal RING domain binds BRCA1 while the BARD1 C-terminal ankyrin and tandem BRCT repeat domains bind CstF-50 to modulate mRNA processing and RNAP II stability in response to DNA damage. Here we characterize the BARD1 structural biochemistry responsible for CstF-50 binding. The crystal structure of the BARD1 BRCT domain uncovers a degenerate phosphopeptide binding pocket lacking the key arginine required for phosphopeptide interactions in other BRCT proteins. Small angle X-ray scattering together with limited proteolysis results indicates that ankyrin and BRCT domains are linked by a flexible tether and do not adopt a fixed orientation relative to one another. Protein pull-down experiments utilizing a series of purified BARD1 deletion mutants indicate that interactions between the CstF-50 WD-40 domain and BARD1 involve the ankyrin-BRCT linker but do not require ankyrin or BRCT domains. The structural plasticity imparted by the ANK-BRCT linker helps to explain the regulated assembly of different protein BARD1 complexes with distinct functions in DNA damage signaling including BARD1-dependent induction of apoptosis plus p53 stabilization and interactions. BARD1 architecture and plasticity imparted by the ANK-BRCT linker are suitable to allow the BARD1 C-terminus to act as a hub with multiple binding sites to integrate diverse DNA damage signals directly to RNA polymerase.