title: Developmentally programmed DNA splicing in Paramecium reveals short-distance crosstalk between DNA cleavage sites.
abstract: Somatic genome assembly in the ciliate Paramecium involves the precise excision of thousands of short internal eliminated sequences (IESs) that are scattered throughout the germline genome and often interrupt open reading frames. Excision is initiated by double-strand breaks centered on the TA dinucleotides that are conserved at each IES boundary, but the factors that drive cleavage site recognition remain unknown. A degenerate consensus was identified previously at IES ends and genetic analyses confirmed the participation of their nucleotide sequence in efficient excision. Even for wild-type IESs, however, variant excision patterns (excised or nonexcised) may be inherited maternally through sexual events, in a homology-dependent manner. We show here that this maternal epigenetic control interferes with the targeting of DNA breaks at IES ends. Furthermore, we demonstrate that a mutation in the TA at one end of an IES impairs DNA cleavage not only at the mutant end but also at the wild-type end. We conclude that crosstalk between both ends takes place prior to their cleavage and propose that the ability of an IES to adopt an excision-prone conformation depends on the combination of its nucleotide sequence and of additional determinants.
authors.affiliation: Ecole Normale Supérieure, Laboratoire de Génétique Moléculaire, 75005 Paris, France.
authors.forename: Ariane
authors.initials: A
authors.lastname: Gratias
authors.forename: Gersende
authors.initials: G
authors.lastname: Lepère
authors.forename: Olivier
authors.initials: O
authors.lastname: Garnier
authors.forename: Sarah
authors.initials: S
authors.lastname: Rosa
authors.forename: Sandra
authors.initials: S
authors.lastname: Duharcourt
authors.forename: Sophie
authors.initials: S
authors.lastname: Malinsky
authors.forename: Eric
authors.initials: E
authors.lastname: Meyer
authors.forename: Mireille
authors.initials: M
authors.lastname: Bétermier
mesh_terms: D020856:AT Rich Sequence; D000818:Animals; D016054:DNA, Protozoan / Q000737:chemistry / Q000378:metabolism*; D044127:Epigenesis, Genetic; D048648:Macronucleus / Q000235:genetics; D008957:Models, Genetic; D009690:Nucleic Acid Conformation; D016805:Paramecium tetraurelia / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D017354:Point Mutation
chemical_list: D016054:DNA, Protozoan