Topoisomerase-II-mediated DNA cleavage within the human ribosomal genes.
The interaction of topoisomerase II (topo II) with human ribosomal DNA (rDNA) was investigated in vivo using the antitumoral drug VM26, a specific inhibitor of topo II, that stabilizes the transient cleavable complex. rDNA-protein complexes isolated from nucleoli of TG cells were analyzed for double strand breaks with probes that covered almost all intergenic transcribed spacer (IGS) and all transcribed sequences of tandem repeat ribosomal DNA genes. Preferential cleavage sites were present in only a part of nucleolar rDNA, i.e., the transcribed region. Proteins, purified from the same complexes, were analyzed by Western-blot and stained by an antiserum against both topo II forms, showing the presence of topo II beta.
Govoni
M
M
Istituto di Biochimica delle Proteine ed Enzimologia, CNR, Napoli, Italy.
Neri
S
S
Labella
T
T
Sylvester
J E
JE
Novello
F
F
Pession
A
A
D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000302:isolation & purification / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology*; D006801:Humans; D007438:Introns; D015183:Restriction Mapping; D059005:Topoisomerase II Inhibitors; D014158:Transcription, Genetic
D004275:DNA, Ribosomal; D059005:Topoisomerase II Inhibitors; D005047:Etoposide; D004247:DNA; D004250:DNA Topoisomerases, Type II