Article
- The EMBO Journal (2001) 20, 3251 - 3261
- doi:10.1093/emboj/20.12.3251
Product analysis illuminates the final steps of IES deletion in Tetrahymena thermophila
Sergei V. Saveliev1 and Michael M. Cox1
- Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706-1544, USA
Correspondence to:
Michael M. Cox, E-mail: cox@biochem.wisc.edu
Received 15 January 2001; Accepted 20 April 2001; Revised 20 April 2001
Abstract
DNA sequences (IES elements) eliminated from the developing macronucleus in the ciliate Tetrahymena thermophila are released as linear fragments, which have now been detected and isolated. A PCR-mediated examination of fragment end structures reveals three types of strand scission events, reflecting three steps in the deletion process. New evidence is provided for two steps proposed previously: an initiating double-stranded cleavage, and strand transfer to create a branched deletion intermediate. The fragment ends provide evidence for a previously uncharacterized third step: the branched DNA strand is cleaved at one of several defined sites located within 15–16 nucleotides of the IES boundary, liberating the deleted DNA in a linear form.
Keywords:
- ciliated protozoa,
- developmentally programmed genome rearrangements,
- DNA cleavage,
- DNA recombination,
- IES element
