Unwinding of chromatin by the SV40 large T antigen DNA helicase.

Ramsperger, Uwe; Stahl, Hans

doi:10.1002/j.1460-2075.1995.tb07324.x

Cited by 54 publications

(50 citation statements)

References 99 publications

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“…Chromatinremodeling machines like SWI͞SNF, whose motor subunits are members of the helicase family of proteins, are known to modify the structure of nucleosomes by perturbing DNA-protein interactions and by inducing topological changes in nucleosomal DNA that are conducive to transcriptional activation (25,26). Likewise, other members of the helicase family which, unlike chromatin-remodeling machines, possess a strand-separating activity, also have been found to destabilize nucleosome structure (27,28). Single-molecule mechanical techniques should be powerful tools for the study of chromatin and these molecular modifiers of its structure.…”

Section: Resultsmentioning

confidence: 99%

Mechanical disruption of individual nucleosomes reveals a reversible multistage release of DNA

Brower-Toland

Smith

Yeh

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

448

465

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The dynamic structure of individual nucleosomes was examined by stretching nucleosomal arrays with a feedback-enhanced optical trap. Forced disassembly of each nucleosome occurred in three stages. Analysis of the data using a simple worm-like chain model yields 76 bp of DNA released from the histone core at low stretching force. Subsequently, 80 bp are released at higher forces in two stages: full extension of DNA with histones bound, followed by detachment of histones. When arrays were relaxed before the dissociated state was reached, nucleosomes were able to reassemble and to repeat the disassembly process. The kinetic parameters for nucleosome disassembly also have been determined.

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Section: Resultsmentioning

confidence: 99%

Mechanical disruption of individual nucleosomes reveals a reversible multistage release of DNA

Brower-Toland

Smith

Yeh

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

448

465

View full text Add to dashboard Cite

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“…This obstacle may be overcome by recruitment of AL1 to its binding site in the 5Ј intergenic region (Fontes et al, 1992) followed by interaction with H3 to alter or displace nucleosomes and allow access of the replication and transcription machinery. Replication of the SV40 minichromosome is facilitated by neutralization of histone charge (Alexiadis et al, 1997) and remodeling of minichromosome structure through the interactions of large T antigen with histones H1 and H3 (Ramsperger and Stahl, 1995). AL1 also interacts with GRIMP, a protein that includes a kinesin domain, a central region that binds to cdc2a, and a C-terminal domain that is unique.…”

Section: Discussionmentioning

confidence: 99%

A Geminivirus Replication Protein Interacts with a Protein Kinase and a Motor Protein That Display Different Expression Patterns during Plant Development and Infection

2002

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The geminivirus protein AL1 initiates viral DNA replication, regulates its own expression, and induces plant gene transcription. To better understand how AL1 interacts with host proteins during these processes, we used yeast two-hybrid library screening and a baculovirus protein interaction system to identify plant proteins that interact with AL1. These studies identified a Ser/Thr kinase, a kinesin, and histone H3 as AL1 partners. The kinase is autophosphorylated and can phosphorylate common kinase substrates in vitro. The kinesin is phosphorylated in insect cells by a cyclin-dependent kinase. Immunostaining of Nicotiana benthamiana and Arabidopsis showed that kinase protein levels and subcellular location are regulated during plant development and geminivirus infection. By contrast, the kinesin is ubiquitous even though it is associated with the spindle apparatus in mitotic cells. Together, our results establish that AL1 interacts with host proteins involved in plant cell division and development. Possible functions of these host factors in healthy and geminivirus-infected plants are discussed.

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“…The packaging of DNA into chromatin restrains approximately one negativesupercoil on the surface of each nucleosome (51). This packaging may hinder the operation of topoisomerases and delay the relief or transmission of torsional strain (55). Inhibitors of topoisomerases I and II freeze these enzymes as protein-DNA complexes at various steps in their reaction pathways (31,49).…”

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confidence: 99%

Transcriptional Consequences of Topoisomerase Inhibition

Collins

Weber

Levens

2001

Molecular and Cellular Biology

112

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In principle, the generation, transmission, and dissipation of supercoiling forces are determined by the arrangement of the physical barriers defining topological boundaries and the disposition of enzymes creating (polymerases and helicases, etc.) or releasing (topoisomerases) torsional strain in DNA. These features are likely to be characteristic for individual genes. By using topoisomerase inhibitors to alter the balance between supercoiling forces in vivo, we monitored changes in the basal transcriptional activity and DNA conformation for several genes. Every gene examined displayed an individualized profile in response to inhibition of topoisomerase I or II. The expression changes elicited by camptothecin (topoisomerase I inhibitor) or adriamycin (topoisomerase II inhibitor) were not equivalent. Camptothecin generally caused transcription complexes to stall in the midst of transcription units, while provoking little response at promoters. Adriamycin, in contrast, caused dramatic changes at or near promoters and prevented transcription. The response to topoisomerase inhibition was also context dependent, differing between chromosomal or episomal c-myc promoters. In addition to being well-characterized DNA-damaging agents, topoisomerase inhibitors may evoke a biological response determined in part from transcriptional effects. The results have ramifications for the use of these drugs as antineoplastic agents.Transcription, replication, recombination, DNA repair, and DNA compaction generate torsional stress in prokaryotic and eukaryotic chromosomes and episomes. This stress must either be accommodated by conformational changes in DNA structure (e.g., supercoils) or else dissipated. If not dissipated, high levels of torsional stress can halt RNA polymerase and deform chromosomal structure (4). Torsional stress may be dissipated by rotation of a free DNA end, i.e., chromosome termini or strand breaks. Alternatively, stresses accumulating within topological domains may be dissipated by topoisomerases. A topological domain is formed whenever both ends of an intact DNA segment are restricted from rotating relative to each other. The boundaries of these domains may be delimited by DNA loops via protein-protein interactions or tethering of DNA to an immobile matrix or scaffold. The energy required to rotate a large, free-ended DNA segment with bound proteins through a viscous medium may become so great that torsional strain accumulates within a pseudo-domain bounded at one end by a kinetic barrier (40). Topological microdomains may be nested within larger and larger macrodomains (24, 70). These domains may be short-lived or stable, depending on the nature of the particular protein-protein and protein-nucleic acid interactions creating their boundaries. A loop formed between a DNA-bound factor and a complex tracking along and around the double helix, such as RNA polymerase II, creates a mobile boundary. Little is known about the arrangement, interlinks, and transmission of torsional stress between topological domains i...

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Unwinding of chromatin by the SV40 large T antigen DNA helicase.

Cited by 54 publications

References 99 publications

Mechanical disruption of individual nucleosomes reveals a reversible multistage release of DNA

Mechanical disruption of individual nucleosomes reveals a reversible multistage release of DNA

A Geminivirus Replication Protein Interacts with a Protein Kinase and a Motor Protein That Display Different Expression Patterns during Plant Development and Infection

Transcriptional Consequences of Topoisomerase Inhibition

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