Document Detail

Type II topoisomerase activities in both the G1 and G2/M phases of the dinoflagellate cell cycle.
MedLine Citation:
PMID:  16252092     Owner:  NLM     Status:  MEDLINE    
Dinoflagellate genomes are large (up to 200 pg) and are encoded in histoneless chromosomes that are quasi-permanently condensed. This unique combination of chromosomal characteristics presents additional topological and cell cycle control problems for a eukaryotic cell, potentially exhibiting novel regulatory requirements of topoisomerase II. The heterotrophic dinoflagellate Crypthecodinium cohnii was used in this study. The topoisomerase II activities throughout its cell cycle were investigated by DNA flow cytometry following enzyme deactivation. Fluorescence microscopy was also used for studying the chromosome morphology of the treated cells. Two classes of topoisomerase II inhibitors were applied in our study, both of which caused G1 delay as well as G2/M arrest in the C. cohnii cell cycle. At high doses, the topoisomerase poisons amsacrine and ellipticine induced DNA fragmentation in C. cohnii cells. Topoisomerase II activities, as measured by the ability to decatenate kinetoplastid DNA (kDNA), are normally detected throughout the cell cycle in C. cohnii. Our results suggest that the requirement of type II topoisomerase activities during the G1 phase of the cell cycle may relate to the unwinding of quasi-permanently condensed chromosomes for the purpose of transcription. This was also the first time that topoisomerase II activity in dinoflagellate cells was detected.
Carmen K M Mak; Victor K L Hung; Joseph T Y Wong
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-11-15
Journal Detail:
Title:  Chromosoma     Volume:  114     ISSN:  0009-5915     ISO Abbreviation:  Chromosoma     Publication Date:  2005 Dec 
Date Detail:
Created Date:  2005-11-18     Completed Date:  2006-02-16     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985138R     Medline TA:  Chromosoma     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  420-31     Citation Subset:  IM    
Biology Department, Hong Kong University of Science and Technology, Clearwater Bay, Kowloon, Hong Kong SAR, People's Republic of China.
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MeSH Terms
Amsacrine / pharmacology
Cell Cycle / drug effects,  physiology*
Chromosomes / drug effects,  ultrastructure*
DNA Damage
DNA Fragmentation / drug effects
DNA Topoisomerases, Type II / antagonists & inhibitors,  metabolism*
Dinoflagellida / cytology*,  enzymology*
Dose-Response Relationship, Drug
Ellipticines / pharmacology
Enzyme Inhibitors / pharmacology
Piperazines / pharmacology
Reg. No./Substance:
0/Ellipticines; 0/Enzyme Inhibitors; 0/Piperazines; 21416-68-2/ICRF 193; 51264-14-3/Amsacrine; 519-23-3/ellipticine; EC Topoisomerases, Type II
Erratum In:
Chromosoma. 2006 Aug;115(4):341

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