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Distinct localizations and patterns of expression of two mitochondrial DNA ligases in Crithidia fasciculata
Author(s) -
Ray Dan S.,
Sinha Krishna Murari,
Hines Jane C.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a511-c
Subject(s) - crithidia fasciculata , mitochondrial dna , biology , expression (computer science) , dna , microbiology and biotechnology , genetics , computational biology , gene , computer science , programming language
The mitochondrial DNA in kinetoplastid protozoa is contained in a single highly condensed structure consisting of thousands of minicircles and approximately 25 maxicircles. The disk‐shaped structure is termed kinetoplast DNA or kDNA and is located in the mitochondrial matrix near the basal body. We have previously identified a mitochondrial DNA ligase (LIG kβ) in the trypanosomatid Crithidia fasciculata that localizes to antipodal sites flanking the kDNA disk where several other replication proteins are localized. We describe here a second mitochondrial DNA ligase (LIG kα). LIG kα localizes to the kinetoplast primarily in cells that have completed mitosis and contain either a dividing kinetoplast or two newly divided kinetoplasts. Essentially all dividing or newly divided kinetoplasts show localization of LIG kα. The ligase is present on both faces of the kDNA disk and at a high level in the kineto‐flagellar zone of the mitochondrial matrix. Cells containing a single nucleus show localization of the LIG kα to the kDNA but at a much lower frequency. The mRNA level of LIG kα varies during the cell cycle out of phase with that of LIG kβ. LIG kα transcript levels are maximal during the phase when cells contain two nuclei whereas LIG kβ transcript levels are maximal during S phase. The LIG kα protein decays with a half‐life of 100 min in the absence of protein synthesis. The periodic expression of the LIG kα transcript and the instability of the LIG kα protein suggest a possible role of the ligase in regulating minicircle replication. Supported by NIH grant GM53254.