Originally published as Genetics Published Articles Ahead of Print on June 14, 2005.

Genetics, Vol. 170, 1623-1631, August 2005, Copyright © 2005
doi:10.1534/genetics.104.031435

Genome-Wide Characterization of Tetrahymena thermophila Chromosome Breakage Sites. II. Physical and Genetic Mapping

Donna Cassidy-Hanley^*, Yelena Bisharyan^*, Vladimir Fridman^*,1, Joseph Gerber, Cindy Lin^,2, Eduardo Orias, Judith D. Orias, Hilary Ryder^,3, Linh Vong^,4 and Eileen P. Hamilton^,5

^* Department of Microbiology and Immunology, Cornell University, Ithaca, New York 14853
Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, California 93106

⁵ Corresponding author: Department of Molecular Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106.
E-mail: ehamilto{at}lifesci.ucsb.edu

The chromosomes of the macronuclear (expressed) genome of Tetrahymena thermophila are generated by developmental fragmentation of the five micronuclear (germline) chromosomes. This fragmentation is site specific, directed by a conserved chromosome breakage sequence (Cbs element). An accompanying article in this issue reports the development of a successful scheme for the genome-wide cloning and identification of functional chromosome breakage sites. This article reports the physical and genetic characterization of 30 functional chromosome breakage junctions. Unique sequence tags and physical sizes were obtained for the pair of macronuclear chromosomes generated by fragmentation at each Cbs. Cbs-associated polymorphisms were used to genetically map 11 junctions to micronuclear linkage groups and macronuclear coassortment groups. Two pairs of junctions showed statistically significant similarity of the sequences flanking the Cbs, suggestive of relatively recent duplications of entire Cbs junctions during Tetrahymena genome evolution. Two macronuclear chromosomes that lose at least one end in an age-related manner were also identified. The whole-genome shotgun sequencing of the Tetrahymena macronucleus has recently been completed at The Institute for Genome Research (TIGR). By providing unique sequence from natural ends of macronuclear chromosomes, Cbs junctions will provide useful sequence tags for relating macro- and micronuclear genetic, physical, and whole-genome sequence maps.

This article has been cited by other articles:

				E. P. Hamilton, S. Williamson, S. Dunn, V. Merriam, C. Lin, L. Vong, J. Russell-Colantonio, and E. Orias The Highly Conserved Family of Tetrahymena thermophila Chromosome Breakage Elements Contains an Invariant 10-Base-Pair Core. Eukaryot. Cell, April 1, 2006; 5(4): 771 - 780. [Abstract] [Full Text] [PDF]

				J. S. Yakisich and G. M. Kapler Deletion of the Tetrahymena thermophila rDNA replication fork barrier region disrupts macronuclear rDNA excision and creates a fragile site in the micronuclear genome Nucleic Acids Res., January 30, 2006; 34(2): 620 - 634. [Abstract] [Full Text] [PDF]

				E. Hamilton, P. Bruns, C. Lin, V. Merriam, E. Orias, L. Vong, and D. Cassidy-Hanley Genome-Wide Characterization of Tetrahymena thermophila Chromosome Breakage Sites. I. Cloning and Identification of Functional Sites Genetics, August 1, 2005; 170(4): 1611 - 1621. [Abstract] [Full Text] [PDF]

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