期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 280, 期 17, 页码 17076-17083出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M413483200
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资金
- NCI NIH HHS [CA74175-07] Funding Source: Medline
- NIGMS NIH HHS [GM62235] Funding Source: Medline
Poly(ADP-ribose) polymerase-1 (PARP-1) is an intracellular sensor of DNA strand breaks and plays a critical role in cellular responses to DNA damage. In normally functioning cells, PARP-1 enzymatic activity has been linked to the alterations in chromatin structure associated with gene expression. However, the molecular determinants for PARP-1 recruitment to specific sites in chromatin in the absence of DNA strand breaks remain obscure. Using gel shift and enzymatic footprinting assays and atomic force microscopy, we show that PARP-1 recognizes distortions in the DNA helical backbone and that it binds to three- and four-way junctions as well as to stably unpaired regions in double-stranded DNA. PARP-1 interactions with non-B DNA structures are functional and lead to its catalytic activation. DNA hairpins, cruciforms, and stably unpaired regions are all effective co-activators of PARP-1 auto-modification and poly( ADP-ribosyl) ation of histone H1 in the absence of free DNA ends. Enzyme kinetic analyses revealed that the structural features of non-B form DNA co-factors are important for PARP-1 catalysis activated by undamaged DNA. K-0.5 constants for DNA co-factors, which are structurally different in the degree of base pairing and spatial DNA organization, follow the order: cruciform <= hairpin << loop. DNA structure also influenced the reaction rate; when a hairpin was substituted with a stably unpaired region, the maximum reaction velocity decreased almost 2-fold. These data suggest a link between PARP-1 binding to non-B DNA structures in genome and its function in the dynamics of local modulation of chromatin structure in the normal physiology of the cell.
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