Open AccessThe kinetoplast structure-specific endonuclease I is related to the 5′ exo/endonuclease domain of bacterial DNA polymerase I and colocalizes with the kinetoplast topoisomerase II and DNA polymerase β during replication
Author(s) -
Michele L. Engel,
Dan S. Ray
Publication year - 1999
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.96.15.8455
Subject(s) - kinetoplast , crithidia fasciculata , biology , dna polymerase , dna polymerase ii , microbiology and biotechnology , minicircle , dna replication , dna clamp , polymerase , okazaki fragments , dna , genetics , eukaryotic dna replication , gene , rna , reverse transcriptase
The mitochondrial DNA (kinetoplast DNA) of the trypanosomatidCrithidia fasciculata has an unusual structure composed of minicircles and maxicircles topologically interlocked into a single network and organized in a disc-shaped structure at the base of the flagellum. We previously purified a structure-specific endonuclease (SSE1), based on its RNase H activity, that is enriched in isolated kinetoplasts. The endonuclease gene has now been cloned, sequenced, and found to be closely related to the 5′ exonuclease domain of bacterial DNA polymerase I proteins. Although the protein does not contain a typical mitochondrial leader sequence, the enzyme is shown to colocalize with a type II DNA topoisomerase and a DNA polymerase β at antipodal sites flanking the kinetoplast disc. Cell synchronization studies with an epitope-tagged construct show that the localization of the endonuclease to the antipodal sites varies in a cell cycle-dependent manner similar to that of the DNA polymerase β [Johnson, C. E. & Englund, P. T. (1998)J. Cell Biol. 143, 911–919]. Immunofluorescent localization of SSE1 to the antipodal sites is only observed during kinetoplast replication. Together, these results suggest a point of control for kinetoplast DNA replication through the regulation of the availability of DNA replication proteins and a possible role for the antipodal sites in removal of RNA primers and the repair of gaps in newly replicated minicircles.