Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Nat Chem Biol. 2013 Mar;9(3):163-8. doi: 10.1038/nchembio.1166. Epub 2013 Jan 20.
Following DNA damage, nuclear p53 induces the expression of PUMA, a BH3-only protein that binds and inhibits the antiapoptotic BCL-2 repertoire, including BCL-xL. PUMA, unique among BH3-only proteins, disrupts the interaction between cytosolic p53 and BCL-xL, allowing p53 to promote apoptosis via direct activation of the BCL-2 effector molecules BAX and BAK. Structural investigations using NMR spectroscopy and X-ray crystallography revealed that PUMA binding induced partial unfolding of two α-helices within BCL-xL. Wild-type PUMA or a PUMA mutant incapable of causing binding-induced unfolding of BCL-xL equivalently inhibited the antiapoptotic BCL-2 repertoire to sensitize for death receptor-activated apoptosis, but only wild-type PUMA promoted p53-dependent, DNA damage-induced apoptosis. Our data suggest that PUMA-induced partial unfolding of BCL-xL disrupts interactions between cytosolic p53 and BCL-xL, releasing the bound p53 to initiate apoptosis. We propose that regulated unfolding of BCL-xL provides a mechanism to promote PUMA-dependent signaling within the apoptotic pathways.
在 DNA 损伤后，核 p53 诱导 PUMA 的表达，PUMA 是一种 BH3 仅蛋白，可结合并抑制抗凋亡 BCL-2 谱，包括 BCL-xL。PUMA 在 BH3 仅蛋白中是独特的，它破坏了细胞质 p53 和 BCL-xL 之间的相互作用，使 p53 通过直接激活 BCL-2 效应分子 BAX 和 BAK 促进细胞凋亡。使用 NMR 光谱和 X 射线晶体学进行的结构研究表明，PUMA 结合诱导 BCL-xL 内两个α螺旋的部分展开。野生型 PUMA 或不能引起 BCL-xL 结合诱导展开的 PUMA 突变体等效地抑制抗凋亡 BCL-2 谱以增强死亡受体激活的细胞凋亡，但只有野生型 PUMA 促进 p53 依赖性、DNA 损伤诱导的细胞凋亡。我们的数据表明，PUMA 诱导的 BCL-xL 部分展开破坏了细胞质 p53 和 BCL-xL 之间的相互作用，释放了结合的 p53 以启动细胞凋亡。我们提出，BCL-xL 的调节展开为促进凋亡途径中 PUMA 依赖性信号提供了一种机制。
