title: Identification of a bacterial-like HslVU protease in the mitochondria of Trypanosoma brucei and its role in mitochondrial DNA replication.
abstract: ATP-dependent protease complexes are present in all living organisms, including the 26S proteasome in eukaryotes, Archaea, and Actinomycetales, and the HslVU protease in eubacteria. The structure of HslVU protease resembles that of the 26S proteasome, and the simultaneous presence of both proteases in one organism was deemed unlikely. However, HslVU homologs have been identified recently in some primordial eukaryotes, though their potential function remains elusive. We characterized the HslVU homolog from Trypanosoma brucei, a eukaryotic protozoan parasite and the causative agent of human sleeping sickness. TbHslVU has ATP-dependent peptidase activity and, like its bacterial counterpart, has essential lysine and N-terminal threonines in the catalytic subunit. By epitope tagging, TbHslVU localizes to mitochondria and is associated with the mitochondrial genome, kinetoplast DNA (kDNA). RNAi of TbHslVU dramatically affects the kDNA by causing over-replication of the minicircle DNA. This leads to defects in kDNA segregation and, subsequently, to continuous network growth to an enormous size. Multiple discrete foci of nicked/gapped minicircles are formed on the periphery of kDNA disc, suggesting a failure in repairing the gaps in the minicircles for kDNA segregation. TbHslVU is a eubacterial protease identified in the mitochondria of a eukaryote. It has a novel function in regulating mitochondrial DNA replication that has never been observed in other organisms.
authors.affiliation: Department of Pharmaceutical Chemistry, University of California, San Francisco, California, United States of America.
authors.forename: Ziyin
authors.initials: Z
authors.lastname: Li
authors.forename: Megan E
authors.initials: ME
authors.lastname: Lindsay
authors.forename: Shawn A
authors.initials: SA
authors.lastname: Motyka
authors.forename: Paul T
authors.initials: PT
authors.lastname: Englund
authors.forename: Ching C
authors.initials: CC
authors.lastname: Wang
mesh_terms: D000818:Animals; D004261:DNA Replication; D018105:DNA, Kinetoplast / Q000235:genetics; D004272:DNA, Mitochondrial / Q000096:biosynthesis*; D049071:Endopeptidase Clp / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D020868:Gene Silencing; D017404:In Situ Hybridization, Fluorescence; D008928:Mitochondria / Q000737:chemistry / Q000201:enzymology*; D015336:Molecular Probe Techniques; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000235:genetics / Q000378:metabolism*
chemical_list: C483566:ClpYQ protease, E coli; D018105:DNA, Kinetoplast; D004272:DNA, Mitochondrial; D029968:Escherichia coli Proteins; D034741:RNA, Small Interfering; D049071:Endopeptidase Clp