A leucine aminopeptidase is involved in kinetoplast DNA segregation in Trypanosoma brucei.

Priscila Peña-Diaz,Marie Vancová,Julius Lukeš,Mark C Field,Christian Resl,Vivian Bellofatto

doi:10.1371/journal.ppat.1006310

Abstract

The kinetoplast (k), the uniquely packaged mitochondrial DNA of trypanosomatid protists is formed by a catenated network of minicircles and maxicircles that divide and segregate once each cell cycle. Although many proteins involved in kDNA replication and segregation are now known, several key steps in the replication mechanism remain uncharacterized at the molecular level, one of which is the nabelschnur or umbilicus, a prominent structure which in the mammalian parasite Trypanosoma brucei connects the daughter kDNA networks prior to their segregation. Here we characterize an M17 family leucyl aminopeptidase metalloprotease, termed TbLAP1, which specifically localizes to the kDNA disk and the nabelschur and represents the first described protein found in this structure. We show that TbLAP1 is required for correct segregation of kDNA, with knockdown resulting in delayed cytokinesis and ectopic expression leading to kDNA loss and decreased cell proliferation. We propose that TbLAP1 is required for efficient kDNA division and specifically participates in the separation of daughter kDNA networks.

Highlights

Kinetoplast (k) DNA is one of the hallmarks of the family Kinetoplastea, and is a unique form of mitochondrial DNA
Trypanosomes bear a single mitochondrion with its genome arranged as a network of circular molecules. kDNA is essential for the Trypanosoma brucei life cycle, as it is required for proper functioning of the mitochondrion and progression through the insect vector
We report leucine aminopeptidase 1 (LAP1) as the first identified component of the nabelschnur, or umbilicus, a structure observed during the separation of daughter kDNA networks, whose expression is required for correct kinetoplast segregation

Summary

Introduction

Kinetoplast (k) DNA is one of the hallmarks of the family Kinetoplastea, and is a unique form of mitochondrial (mt) DNA. Unlike the mt DNA of most eukaryotes, kDNA divides once per cell cycle. Whilst this occurs immediately prior to nuclear DNA synthesis, replication of kDNA is in synchrony with nuclear division [3]. In T. brucei, kDNA is essential for mt functions, recently specific mutations have been described that can facilitate viability without kDNA [4]. This is not the case for most infective strains found in the field, as treatment with ethidium bromide, which leads to kDNA loss, proves effective in controlling the spread of the parasite among cattle [5]

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