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

  1. 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


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