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DNA interstrand crosslinks (ICLs) are highly toxic because they block the progression of replisomes. The Fanconi Anemia (FA) proteins, encoded by genes that are mutated in FA, are important for repair of ICLs. The FA core complex catalyzes the monoubiquitination of FANCD2, and this event is essential for several steps of ICL repair. However, how(More)
The Holliday (four-way) junction is a critical intermediate in homologous genetic recombination. We have studied the structure of a series of four-way junctions, constructed by hybridization of four 80 nucleotide synthetic oligonucleotides. These molecules migrate anomalously slowly in gel electrophoresis. Each arm of any junction could be selectively(More)
Repeat tracts of guanine bases found in DNA and RNA can form tetraplex structures in the presence of a variety of monovalent cations. Evidence suggests that guanine tetraplexes assume important functions within chromosomal telomeres, immunoglobulin switch regions, and the human immunodeficiency virus genome. The structure of a parallel-stranded tetraplex(More)
Holliday junctions (HJs) are X-shaped DNA structures that arise during homologous recombination, which must be removed to enable chromosome segregation. The SLX1 and MUS81-EME1 nucleases can both process HJs in vitro, and they bind in close proximity on the SLX4 scaffold, hinting at possible cooperation. However, the cellular roles of mammalian SLX1 are not(More)
ATP-dependent chromatin remodeling activities participate in the alteration of chromatin structure during gene regulation. All have DNA- or chromatin-stimulated ATPase activity and many can alter the structure of chromatin; however, the means by which they do this have remained unclear. Here we describe a novel activity for ATP-dependent chromatin(More)
Despite the recent advances in single-molecule manipulation techniques, purely mechanical approaches cannot detect subtle conformational changes in the biologically important regime of weak forces. We developed a hybrid scheme combining force and fluorescence that allowed us to examine the effect of subpiconewton forces on the nanometer scale motion of the(More)
The k-turn is a widespread structural motif that introduces a tight kink into the helical axis of double-stranded RNA. The adenine bases of consecutive G•A pairs are directed toward the minor groove of the opposing helix, hydrogen bonding in a typical A-minor interaction. We show here that the available structures of k-turns divide into two classes,(More)
The kink turn is a widespread RNA motif that introduces an acute kink into the axis of duplex RNA, typically comprising a bulge followed by a G⋅A and A⋅G pairs. The kinked conformation is stabilized by metal ions, or the binding of proteins including L7Ae. We now demonstrate a third mechanism for the stabilization of k-turn structure, involving tertiary(More)
The ion-induced folding transitions of the hammerhead ribozyme have been analysed by fluorescence resonance energy transfer. The hammerhead ribozyme may be regarded as a special example of a three-way RNA junction, the global structure of which has been studied by comparing the distances (as energy transfer efficiencies) between the ends of pairs of(More)