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Molecular and Cellular Biology, July 2006, p. 5382-5393, Vol. 26, No. 14
0270-7306/06/$08.00+0     doi:10.1128/MCB.00369-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Role of p38 in Replication of Trypanosoma brucei Kinetoplast DNA

Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205,¹ Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599²

Received 1 March 2006/ Returned for modification 29 March 2006/ Accepted 5 May 2006

Trypanosomes have an unusual mitochondrial genome, called kinetoplast DNA, that is a giant network containing thousands of interlocked minicircles. During kinetoplast DNA synthesis, minicircles are released from the network for replication as -structures, and then the free minicircle progeny reattach to the network. We report that a mitochondrial protein, which we term p38, functions in kinetoplast DNA replication. RNA interference (RNAi) of p38 resulted in loss of kinetoplast DNA and accumulation of a novel free minicircle species named fraction S. Fraction S minicircles are so underwound that on isolation they become highly negatively supertwisted and develop a region of Z-DNA. p38 binds to minicircle sequences within the replication origin. We conclude that cells with RNAi-induced loss of p38 cannot initiate minicircle replication, although they can extensively unwind free minicircles.

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