C. Hamelin et al., DNA TOPOISOMERASE ACTIVITY ASSOCIATED WITH SIMIAN-VIRUS-40 NUCLEOPROTEIN COMPLEXES, Biochemistry and cell biology, 72(5-6), 1994, pp. 195-201
Simian virus 40 (SV40) chromatin extracted from nuclei of infected mon
key cells (CV1) was sedimented in neutral sucrose gradients, before an
d after digestion with bovine pancreatic RNase I-A or DNase I. DNA top
oisomerase (TI) activity was found associated with RNase-resistant, DN
ase-sensitive SV40 nucleoprotein complexes. After polyacrylamide gel e
lectrophoresis, a number of proteins with a molecular mass between 40
and 70 kDa were seen at the level of viral DNA peaks, some of which ma
y represent catalytically active breakdown products of the TI enzyme.
Large protein complexes were observed under the electron microscope in
association with the viral chromosomes and appear to correspond to th
e SV40 DNA replication complex, including TI. Our results suggest that
TI activity is indeed associated with the viral minichromosomes under
going replication in vivo.