The nature of DNA plays a role in chromosome segregation: endoreduplication in halogen-substituted chromosomes.
AA8 Chinese hamster ovary cells were treated with halogenated nucleosides analogues of thymidine, namely CldU, 5-iodo-2'-deoxyuridine (IdU), and 5-bromo-2'-deoxyuridine (BrdU), following different experimental protocols. The purpose was to see whether incorporation of exogenous pyrimidine analogues into DNA could interfere with normal chromosome segregation. The endpoint chosen was endoreduplication, that arises after aberrant mitosis when daughter chromatids segregation fails. Treatment with any of the halogenated nucleosides for two consecutive cell cycles resulted in endoreduplication, with a highest yield for CldU, intermediate for IdU, and lowest for BrdU. The frequency of endoreduplicated cells paralleled in all cases the level of analogue substitution into DNA. Our results seem to support that thymidine analogue substitution into DNA is responsible for the triggering of endoreduplication. Besides, the lack of any effect on endoreduplication when CldU was present for only one S-period strongly suggest that it is the nature of template, and not nascent DNA, that plays a major role in chromosome segregation. Taking into account that topoisomerase II cleaves DNA at preferred sequences within its recognition/binding sites, the likely involvement of the enzyme is discussed.
Cortés
Felipe
F
Department of Cell Biology, Faculty of Biology, Avenida Reina Mercedes, 6. E-41012, Seville, Spain. cortes@us.es
Pastor
Nuria
N
Mateos
Santiago
S
Domínguez
Inmaculada
I
D000818:Animals; D016466:CHO Cells; D020090:Chromosome Segregation / Q000502:physiology*; D002875:Chromosomes / Q000502:physiology*; D006224:Cricetinae; D004247:DNA / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D006219:Halogens / Q000378:metabolism*; D013936:Thymidine / Q000031:analogs & derivatives
D006219:Halogens; D004247:DNA; D004250:DNA Topoisomerases, Type II; D013936:Thymidine