Affiliation:
1. Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, UCLA, Los Angeles, California 90095-1570
Abstract
ABSTRACT
The mitochondrial DNA of trypanosomes contains two types of circular DNAs, minicircles and maxicircles. Both minicircles and maxicircles replicate from specific replication origins by unidirectional theta-type intermediates. Initiation of the minicircle leading strand and also that of at least the first Okazaki fragment involve RNA priming. The
Trypanosoma brucei
genome encodes two mitochondrial DNA primases, PRI1 and PRI2, related to the primases of eukaryotic nucleocytoplasmic large DNA viruses. These primases are members of the archeoeukaryotic primase superfamily, and each of them contain an RNA recognition motif and a PriCT-2 motif. In
Leishmania
species, PRI2 proteins are approximately 61 to 66 kDa in size, whereas in
Trypanosoma
species, PRI2 proteins have additional long amino-terminal extensions. RNA interference (RNAi) of
T. brucei PRI2
resulted in the loss of kinetoplast DNA and accumulation of covalently closed free minicircles. Recombinant PRI2 lacking this extension (PRI2ΔNT) primes poly(dA) synthesis on a poly(dT) template in an ATP-dependent manner. Mutation of two conserved aspartate residues (PRI2ΔNTCS) resulted in loss of enzymatic activity but not loss of DNA binding. We propose that PRI2 is directly involved in initiating kinetoplast minicircle replication.
Publisher
American Society for Microbiology
Subject
Molecular Biology,General Medicine,Microbiology
Cited by
31 articles.
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