title: Product analysis illuminates the final steps of IES deletion in Tetrahymena thermophila.
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.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706-1544, USA.
authors.forename: S V
authors.initials: SV
authors.lastname: Saveliev
authors.forename: M M
authors.initials: MM
authors.lastname: Cox
mesh_terms: D000818:Animals; D016054:DNA, Protozoan / Q000737:chemistry; D009690:Nucleic Acid Conformation; D017384:Sequence Deletion; D016808:Tetrahymena thermophila / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan