S. Wolfl et al., IDENTIFICATION OF PROCESSES THAT INFLUENCE NEGATIVE SUPERCOILING IN THE HUMAN C-MYC GENE, Biochimica et biophysica acta, N. Gene structure and expression, 1352(2), 1997, pp. 213-221
DNA elements with sequences suitable for Z-DNA formation are found fre
quently at various positions in chromatin. Z-DNA formation in these se
quences depends lamely on the level of local negative supercoiling. We
can use binding of a Z-DNA specific antibody at low concentrations in
metabolically active permeabilized nuclei to detect naturally occurri
ng Z-DNA formation. Previously we identified three sequence elements i
n the human c-myc gene that adopt the Z-DNA conformation in the transc
ribed gene. The three elements are found far upstream (Z1), close to t
he main transcription start site (Z2) and in the first intron (Z3). He
re we measure the persistence of Z-DNA at these three sites under the
influence of various metabolic inhibitors. This provides some insight
into the varying levels of negative supercoiling. alpha-Amanitin, an i
nhibitor of transcription, reduced the persistence of Z-DNA in all thr
ee elements. Aphidicolin, an inhibitor of replication, increased the p
ersistence of Z-DNA in one element without significantly influencing t
he other two elements. When camptothecin an inhibitor of topoisomerase
I was added in the presence of alpha-amanitin, the persistence of Z-D
NA was extended in all three elements. However, in the presence of aph
idicolin no effect of camptothecin on Z-DNA formation was observed. (C
) 1997 Elsevier Science B.V.