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Int J Dev Biol February 1, 1996; 40 (1): 239-44.
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Localization of a high molecular weight form of DNA topoisomerase I in amphibian oocytes.

Gebauer D , Mais C , Zinger K , Hock R , Lieb B , Scheer U .

Xenopus oocytes express a 165 kDa variant of DNA topoisomerase I (topo I) as opposed to the canonical 110 kDa form of somatic cells (Richard and Bogenhagen, Dev. Biol. 146: 4-11, 1991). By immunofluorescence microscopy using variant-specific antibodies we show that this high molecular weight form is associated with lampbrush chromosome loops and the inner regions of the amplified nucleoli. Inhibition of topo I-activity by either Camptothecin-treatment or microinjection of neutralizing antibodies resulted in loop retraction and the condensation of chromosomes and amplified nucleoli. These data indicate that the oocyte-specific 165 kDa form of topo I is involved in transcriptional processes mediated by RNA polymerase I and II and is therefore functionally equivalent to the somatic cell 110 kDa counterpart.

PubMed ID: 8735934
Article link: Int J Dev Biol

Species referenced: Xenopus laevis
Genes referenced: top1.1

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