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Eukaryotic Cell doi:10.1128/EC.00284-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification of New Kinetoplast DNA Replication Proteins in Trypanosomatids Based on Predicted S-phase Expression and Mitochondrial Targeting

Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, UCLA, Los Angeles, CA 90095-1570

^* To whom correspondence should be addressed. Email: danray{at}ucla.edu.

	Abstract

Trypanosomatid parasites contain an unusual form of mitochondrial DNA (kDNA) consisting of a catenated network of several thousand minicircles and a smaller number of maxicircles. Many of the proteins involved in the replication and division of kDNA are likely to have no counterparts in other organisms and would not be identified by similarity to known replication proteins in other organisms. A new kDNA replication protein conserved in kinetoplastids has been identified based on the presence of post-transcriptional regulatory sequences associated with S-phase gene expression and predicted mitochondrial targeting. The Leishmania major protein P105 and Trypanosoma brucei protein P93 localize to antipodal sites flanking the kDNA disk where several other replication proteins and nascent minicircles have been localized. Like some of these kDNA replication proteins, the LmP105 protein is only present at the antipodal sites during S phase. RNA interference (RNAi) of TbP93 expression resulted in a cessation of cell growth and the loss of kDNA. Nicked/gapped forms of minicircles, the products of minicircle replication, were preferentially lost from the population of free minicircles during RNAi suggesting an involvement of TbP93 in minicircle replication. This approach should allow the identification of other novel proteins involved in the duplication of kDNA.