title: A Parallel G Quadruplex-Binding Protein Regulates the Boundaries of DNA Elimination Events of Tetrahymena thermophila.
abstract: Guanine (G)-rich DNA readily forms four-stranded quadruplexes in vitro, but evidence for their participation in genome regulation is limited. We have identified a quadruplex-binding protein, Lia3, that controls the boundaries of germline-limited, internal eliminated sequences (IESs) of Tetrahymena thermophila. Differentiation of this ciliate's somatic genome requires excision of thousands of IESs, targeted for removal by small-RNA-directed heterochromatin formation. In cells lacking LIA3 (ΔLIA3), the excision of IESs bounded by specific G-rich polypurine tracts was impaired and imprecise, whereas the removal of IESs without such controlling sequences was unaffected. We found that oligonucleotides containing these polypurine tracts formed parallel G-quadruplex structures that are specifically bound by Lia3. The discovery that Lia3 binds G-quadruplex DNA and controls the accuracy of DNA elimination at loci with specific G-tracts uncovers an unrecognized potential of quadruplex structures to regulate chromosome organization.
authors.affiliation: Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Carle
authors.affiliation: Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Hani S
authors.initials: HS
authors.lastname: Zaher
authors.affiliation: Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America.
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Chalker
mesh_terms: D002875:Chromosomes / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D054856:G-Quadruplexes; D016678:Genome; D009841:Oligonucleotides / Q000235:genetics; D011485:Protein Binding; D015800:Protozoan Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D016615:Telomere / Q000235:genetics; D016808:Tetrahymena thermophila / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D009841:Oligonucleotides; D015800:Protozoan Proteins