Dataset Information

Single-molecule imaging reveals mechanisms of protein disruption by a DNA translocase.

ABSTRACT: In physiological settings, nucleic-acid translocases must act on substrates occupied by other proteins, and an increasingly appreciated role of translocases is to catalyse protein displacement from RNA and DNA. However, little is known regarding the inevitable collisions that must occur, and the fate of protein obstacles and the mechanisms by which they are evicted from DNA remain unexplored. Here we sought to establish the mechanistic basis for protein displacement from DNA using RecBCD as a model system. Using nanofabricated curtains of DNA and multicolour single-molecule microscopy, we visualized collisions between a model translocase and different DNA-bound proteins in real time. We show that the DNA translocase RecBCD can disrupt core RNA polymerase, holoenzymes, stalled elongation complexes and transcribing RNA polymerases in either head-to-head or head-to-tail orientations, as well as EcoRI(E111Q), lac repressor and even nucleosomes. RecBCD did not pause during collisions and often pushed proteins thousands of base pairs before evicting them from DNA. We conclude that RecBCD overwhelms obstacles through direct transduction of chemomechanical force with no need for specific protein-protein interactions, and that proteins can be removed from DNA through active disruption mechanisms that act on a transition state intermediate as they are pushed from one nonspecific site to the next.

SUBMITTER: Finkelstein IJ

PROVIDER: S-EPMC3230117 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Single-molecule imaging reveals mechanisms of protein disruption by a DNA translocase.

Finkelstein Ilya J IJ Visnapuu Mari-Liis ML Greene Eric C EC

Nature 20101124 7326

In physiological settings, nucleic-acid translocases must act on substrates occupied by other proteins, and an increasingly appreciated role of translocases is to catalyse protein displacement from RNA and DNA. However, little is known regarding the inevitable collisions that must occur, and the fate of protein obstacles and the mechanisms by which they are evicted from DNA remain unexplored. Here we sought to establish the mechanistic basis for protein displacement from DNA using RecBCD as a mo ...[more]

PMID: 21107319

Similar Datasets

Project description:DNA breaks can be repaired with high fidelity by homologous recombination. A ubiquitous protein that is essential for this DNA template-directed repair is RecA. After resection of broken DNA to produce single-stranded DNA (ssDNA), RecA assembles on this ssDNA into a filament with the unique capacity to search and find DNA sequences in double-stranded DNA (dsDNA) that are homologous to the ssDNA. This homology search is vital to recombinational DNA repair, and results in homologous pairing and exchange of DNA strands. Homologous pairing involves DNA sequence-specific target location by the RecA-ssDNA complex. Despite decades of study, the mechanism of this enigmatic search process remains unknown. RecA is a DNA-dependent ATPase, but ATP hydrolysis is not required for DNA pairing and strand exchange, eliminating active search processes. Using dual optical trapping to manipulate DNA, and single-molecule fluorescence microscopy to image DNA pairing, we demonstrate that both the three-dimensional conformational state of the dsDNA target and the length of the homologous RecA-ssDNA filament have important roles in the homology search. We discovered that as the end-to-end distance of the target dsDNA molecule is increased, constraining the available three-dimensional (3D) conformations of the molecule, the rate of homologous pairing decreases. Conversely, when the length of the ssDNA in the nucleoprotein filament is increased, homology is found faster. We propose a model for the DNA homology search process termed 'intersegmental contact sampling', in which the intrinsic multivalent nature of the RecA nucleoprotein filament is used to search DNA sequence space within 3D domains of DNA, exploiting multiple weak contacts to rapidly search for homology. Our findings highlight the importance of the 3D conformational dynamics of DNA, reveal a previously unknown facet of the homology search, and provide insight into the mechanism of DNA target location by this member of a universal family of proteins.

Dataset Information

Single-molecule imaging reveals mechanisms of protein disruption by a DNA translocase.

Publications

Single-molecule imaging reveals mechanisms of protein disruption by a DNA translocase.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure