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Eukaryotic Cell, January 2006, p. 54-61, Vol. 5, No. 1
1535-9778/06/$08.00+0     doi:10.1128/EC.5.1.54-61.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Cell Cycle-Dependent Localization and Properties of a Second Mitochondrial DNA Ligase in Crithidia fasciculata

Krishna Murari Sinha, Jane C. Hines, and Dan S. Ray*

Molecular Biology Institute and Department of Microbiology, Immunology and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095

Received 12 August 2005/ Accepted 2 November 2005

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 (kDNA) and is located in the mitochondrial matrix near the basal body. We have previously identified a mitochondrial DNA ligase (LIG kß) 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 k{alpha}). LIG k{alpha} 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 k{alpha}. The ligase is present on both faces of the kDNA disk and at a high level in the kinetoflagellar zone of the mitochondrial matrix. Cells containing a single nucleus show localization of the LIG k{alpha} to the kDNA but at a much lower frequency. The mRNA level of LIG k{alpha} varies during the cell cycle out of phase with that of LIG kß. LIG k{alpha} transcript levels are maximal during the phase when cells contain two nuclei, whereas LIG kß transcript levels are maximal during S phase. The LIG k{alpha} protein decays with a half-life of 100 min in the absence of protein synthesis. The periodic expression of the LIG k{alpha} transcript and the instability of the LIG k{alpha} protein suggest a possible role of the ligase in regulating minicircle replication.

* Corresponding author. Mailing address: 301A Paul D. Boyer Hall, 611 Charles Young Dr. East, UCLA, Los Angeles, CA 90095-1570. Phone: (310) 825-4178. Fax: (310) 206-7286. E-mail: danray{at}ucla.edu.

Eukaryotic Cell, January 2006, p. 54-61, Vol. 5, No. 1
1535-9778/06/$08.00+0     doi:10.1128/EC.5.1.54-61.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Milman, N., Motyka, S. A., Englund, P. T., Robinson, D., Shlomai, J. (2007). Mitochondrial origin-binding protein UMSBP mediates DNA replication and segregation in trypanosomes. Proc. Natl. Acad. Sci. USA 104: 19250-19255 [Abstract] [Full Text]  
  • Li, Y., Sun, Y., Hines, J. C., Ray, D. S. (2007). Identification of New Kinetoplast DNA Replication Proteins in Trypanosomatids Based on Predicted S-Phase Expression and Mitochondrial Targeting. Eukaryot Cell 6: 2303-2310 [Abstract] [Full Text]  


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