title: Characterization of in vivo developmental chromosome fragmentation intermediates in E. crassus.
abstract: Ligation-mediated PCR was used to characterize intermediates in the fragmentation/de novo telomere addition process that occurs during sexual reproduction in the ciliate E. crassus. Fragmentation generates ends with 6-base, 3' overhangs that have 5'-phosphate and 3'-hydroxyl groups. These intermediates are detected only during the period of chromosome fragmentation. Fragmentation always occurs at a precise distance from a conserved sequence, the E-Cbs, indicating that it is a key cis-acting element in the process. The results also serve to identify the natural substrate for de novo telomere addition and indicate that telomerase recognizes, and compensates for, partial telomeric repeats at the ends of fragmentation intermediates. Similarities of the Euplotes fragmentation/telomere addition process to the movement of some non-long terminal repeat retrotransposons are discussed.
authors.affiliation: Department of Biochemistry, University of Connecticut Health Center, Farmington 06032, USA. butcher@panda.uchc.edu
authors.forename: L A
authors.initials: LA
authors.lastname: Klobutcher
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000201:enzymology / Q000235:genetics; D019457:Chromosome Breakage / Q000235:genetics*; D002875:Chromosomes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence / Q000235:genetics; D011088:DNA Ligases / Q000378:metabolism; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016812:Euplotes / Q000166:cytology / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development*; D019143:Evolution, Molecular; D048631:Micronucleus, Germline / Q000201:enzymology / Q000235:genetics; D008957:Models, Genetic; D016133:Polymerase Chain Reaction / Q000379:methods; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012098:Reproduction; D018626:Retroelements / Q000235:genetics; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D016054:DNA, Protozoan; D004277:DNA, Single-Stranded; D018626:Retroelements; D019098:Telomerase; D011088:DNA Ligases