Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Simian virus 40 (SV40) nucleoprotein complexes were studied with the electron microscope. Depending on the isolation procedure, SV40 chromatin has two different conformations: complexes isolated in the presence of 0.15 M NaCl appeared as very compact globular structures, while those isolated in the presence of 0.6 M NaCl had the typical 'beads-on-a-string' appearance of the primary nucleofilament. Concomitant with this structural change was a variation in the histone pattern and sedimentation behaviour of the complexes: with NaCl at 0.15 mol 1(-1) the isolated complexes contained both the nucleosomal histones and histone H1, and sedimented in sucrose gradients at 70S. Increasing the ionic strength to 0.6 M NaCl resulted in the removal of histone H1 from the complexes and in a decrease of the sedimentation coefficient to 40S. DNA relaxing enzyme is associated with the SV40 nucleoprotein complexes. The numbers of superhelical turns in DNA from compact and open types of complexes were found to be the same. Therefore the transition from the condensed to the open structure of viral chromatin does not require a change in the topological winding number of its DNA.
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PMID:The structure of SV 40 chromatin. 2 73

Aldehydes with specific protein-DNA crosslinking ability disrupted simian virus 40 (SV40) DNA replication to cause replication fork failure by the 40S intermediate pathway, in which replicating viral genomes become inactivated and torsionally stressed. In contrast, aldehydes without detectable protein-DNA crosslinking ability had no effect on SV40 DNA replication during the 10 min exposure times employed. This indicates that protein-DNA crosslinks block either DNA polymerase or the entire replication complex. Replication failure by the 40S pathway is known to initiate recombinational events in the damaged SV40 replicons. Similar events in cellular replicons may play a role in the clastogenic effects of formaldehyde. In addition, formaldehyde and acrolein caused accumulation of catenated (topologically linked) SV40 daughter chromosomes--a signature of topoisomerase II inhibition.
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PMID:Aldehyde-induced protein-DNA crosslinks disrupt specific stages of SV40 DNA replication. 820 64