Role of p38 in Replication of Trypanosoma brucei Kinetoplast DNA

Abstract

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 θ-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.

We thank Leroy Liu, Roger MacMacken, and Barbara Sollner-Webb for helpful suggestions and members of our lab for many discussions. We thank Isabelle Coppens and Carol Cooke for help with the EM. We also thank Gokben Yildirir for generous assistance.

This work was supported in part by NIH grants AI058613 to P.T.E. and GM31819 to J.D.G.