Document Detail

Mitochondrial DNA ligases of Trypanosoma brucei.
MedLine Citation:
PMID:  15821136     Owner:  NLM     Status:  MEDLINE    
The mitochondrial DNA of Trypanosoma brucei, termed kinetoplast DNA or kDNA, consists of thousands of minicircles and a small number of maxicircles catenated into a single network organized as a nucleoprotein disk at the base of the flagellum. Minicircles are replicated free of the network but still contain nicks and gaps after rejoining to the network. Covalent closure of remaining discontinuities in newly replicated minicircles after their rejoining to the network is delayed until all minicircles have been replicated. The DNA ligase involved in this terminal step in minicircle replication has not been identified. A search of kinetoplastid genome databases has identified two putative DNA ligase genes in tandem. These genes (LIG k alpha and LIG k beta) are highly diverged from mitochondrial and nuclear DNA ligase genes of higher eukaryotes. Expression of epitope-tagged versions of these genes shows that both LIG k alpha and LIG k beta are mitochondrial DNA ligases. Epitope-tagged LIG k alpha localizes throughout the kDNA, whereas LIG k beta shows an antipodal localization close to, but not overlapping, that of topoisomerase II, suggesting that these proteins may be contained in distinct structures or protein complexes. Knockdown of the LIG k alpha mRNA by RNA interference led to a cessation of the release of minicircles from the network and resulted in a reduction in size of the kDNA networks and rapid loss of the kDNA from the cell. Closely related pairs of mitochondrial DNA ligase genes were also identified in Leishmania major and Crithidia fasciculata.
Nick Downey; Jane C Hines; Krishna M Sinha; Dan S Ray
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Eukaryotic cell     Volume:  4     ISSN:  1535-9778     ISO Abbreviation:  Eukaryotic Cell     Publication Date:  2005 Apr 
Date Detail:
Created Date:  2005-04-11     Completed Date:  2005-08-30     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  101130731     Medline TA:  Eukaryot Cell     Country:  United States    
Other Details:
Languages:  eng     Pagination:  765-74     Citation Subset:  IM    
Molecular Biology Institute and Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095-1570, USA.
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MeSH Terms
Amino Acid Sequence
Cloning, Molecular
DNA Ligases / genetics,  metabolism*
DNA Topoisomerases, Type II / metabolism
DNA, Kinetoplast / genetics,  metabolism*
DNA, Mitochondrial / genetics*
DNA, Protozoan / genetics*
Databases as Topic
Mitochondria / enzymology*
Molecular Sequence Data
RNA Interference
RNA, Messenger / antagonists & inhibitors,  genetics,  metabolism
Sequence Homology, Amino Acid
Trypanosoma brucei brucei / enzymology,  genetics*,  ultrastructure
Grant Support
Reg. No./Substance:
0/DNA, Kinetoplast; 0/DNA, Mitochondrial; 0/DNA, Protozoan; 0/RNA, Messenger; EC Topoisomerases, Type II; EC 6.5.1.-/DNA Ligases

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