title: The Tetrahymena argonaute-binding protein Giw1p directs a mature argonaute-siRNA complex to the nucleus.
abstract: Emerging evidence suggests that RNA interference (RNAi)-related processes act both in the cytoplasm and in the nucleus. However, the process by which the RNAi machinery is transported into the nucleus remains poorly understood. The Tetrahymena Argonaute protein Twi1p localizes to the nucleus and is crucial for small RNA-directed programmed DNA elimination. In this study, we identify Giw1p, which binds to Twi1p and is required for its nuclear localization. Furthermore, the endoribonuclease (Slicer) activity of Twi1p plays a vital role in the removal of one of the two strands of Twi1p-associated small interfering RNAs (siRNAs), leading to a functionally mature Twi1p-siRNA complex. Slicer activity is also shown to be required for nuclear localization of Twi1p and for its association with Giw1p. These results suggest that Giw1p senses the state of Twi1p-associated siRNAs and selectively transports the mature Twi1p-siRNA complex into the nucleus.
authors.affiliation: Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), Dr. Bohr-Gasse 3, A-1030 Vienna, Austria.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Noto
authors.forename: Henriette M
authors.initials: HM
authors.lastname: Kurth
authors.forename: Kensuke
authors.initials: K
authors.lastname: Kataoka
authors.forename: Lucia
authors.initials: L
authors.lastname: Aronica
authors.forename: Leroi V
authors.initials: LV
authors.lastname: DeSouza
authors.forename: K W Michael
authors.initials: KW
authors.lastname: Siu
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Pearlman
authors.forename: Martin A
authors.initials: MA
authors.lastname: Gorovsky
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Mochizuki
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D003227:Conjugation, Genetic; D003593:Cytoplasm / Q000378:metabolism; D039642:Eukaryotic Initiation Factors / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism*; D016808:Tetrahymena thermophila / Q000166:cytology / Q000378:metabolism*; D051879:Twist-Related Protein 1 / Q000378:metabolism
chemical_list: D039642:Eukaryotic Initiation Factors; D015800:Protozoan Proteins; D034741:RNA, Small Interfering; D051879:Twist-Related Protein 1