Intramitochondrial localization of universal minicircle sequence-binding protein, a trypanosomatid protein that binds kinetoplast minicircle replication origins

Kawther Abu-Elneel, Derrick R. Robinson, Mark E. Drew, Paul T. Englund, Joseph Shlomai

Research output: Contribution to journalArticle

Abstract

Kinetoplast DNA (kDNA), the mitochondrial DNA of the trypanosomatid Crithidia fasciculata, is a unique structure containing 5,000 DNA minicircles topologically linked into a massive network. In vivo, the network is condensed into a disk-shaped structure. Replication of minicircles initiates at unique origins that are bound by universal minicircle sequence (UMS)-binding protein (UMSBP), a sequence-specific DNA-binding protein. This protein, encoded by a nuclear gene, localizes within the cell's single mitochondrion. Using immunofluorescence, we found that UMSBP localizes exclusively to two neighboring sites adjacent to the face of the kDNA disk nearest the cell's flagellum. This site is distinct from the two antipodal positions at the perimeter of the disk that is occupied by DNA polymerase β, topoisomerase II, and a structure-specific endonuclease. Although we found constant steady-state levels of UMSBP mRNA and protein and a constant rate of UMSBP synthesis throughout the cell cycle, immunofluorescence indicated that UMSBP localization within the kinetoplast is not static. The intramitochondrial localization of UMSBP and other kDNA replication enzymes significantly clarifies our understanding of the process of kDNA replication.

Original languageEnglish (US)
Pages (from-to)725-733
Number of pages9
JournalJournal of Cell Biology
Volume153
Issue number4
DOIs
StatePublished - May 14 2001

Keywords

  • KDNA replication
  • Kinetoplast DNA
  • UMS-binding protein
  • Universal minicircle sequence

ASJC Scopus subject areas

  • Cell Biology

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