title: Towards novel efficient and stable nuclear import signals: synthesis and properties of trimethylguanosine cap analogs modified within the 5',5'-triphosphate bridge.
abstract: A trimethylguanosine (TMG) cap is present at the 5' end of several small nuclear and nucleolar RNAs. Recently, it has been reported that the TMG cap is a potential nuclear import signal for nucleus-targeting therapeutic nucleic acids and proteins. The import is mediated by recognition of the TMG cap by the snRNA transporting protein, snurportin1. This work describes the synthesis and properties of a series of dinucleotide TMG cap (m3(2,2,7)GpppG) analogs modified in the 5',5'-triphosphate bridge as tools to study TMG cap-dependent biological processes. The bridge was altered at different positions by introducing either bridging (imidodiphosphate, O to NH and methylenebisphosphonate, O to CH2) or non-bridging (phosphorothioate, O to S and boranophosphate, O to BH3) modifications, or by elongation to tetraphosphate. The stability of novel analogs in blood serum was studied to reveal that the α,β-bridging O to NH substitution (m3(2,2,7)GppNHpG) confers the highest resistance. Short RNAs capped with analogs containing α,β-bridging (m3(2,2,7)GppNHpG) or β-non-bridging (m3(2,2,7)GppSpG D2) modifications were resistant to decapping pyrophosphatase, hNudt16. Preliminary studies on binding by human snurportin1 revealed that both O to NH and O to S substitutions support this binding. Due to favorable properties in all three assays, m3(2,2,7)GppNHpG was selected as a promising candidate for further studies on the efficiency of the TMG cap as a nuclear import signal.
authors.affiliation: Division of Biophysics, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Zwirki i Wigury 93, 02-089 Warsaw, Poland. jacekj@biogeo.uw.edu.pl.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Zytek
authors.forename: Joanna
authors.initials: J
authors.lastname: Kowalska
authors.forename: Maciej
authors.initials: M
authors.lastname: Lukaszewicz
authors.forename: Blazej A
authors.initials: BA
authors.lastname: Wojtczak
authors.forename: Joanna
authors.initials: J
authors.lastname: Zuberek
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Ferenc-Mrozek
authors.forename: Edward
authors.initials: E
authors.lastname: Darzynkiewicz
authors.forename: Anna
authors.initials: A
authors.lastname: Niedzwiecka
authors.forename: Jacek
authors.initials: J
authors.lastname: Jemielity
mesh_terms: D021581:Active Transport, Cell Nucleus; D006151:Guanosine / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D015394:Molecular Structure; D011122:Polyphosphates / Q000737:chemistry*; D011485:Protein Binding; D011755:Pyrophosphatases / Q000378:metabolism; D012314:RNA Cap Analogs / Q000138:chemical synthesis* / Q000737:chemistry; D039381:RNA Cap-Binding Proteins / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D011122:Polyphosphates; D012314:RNA Cap Analogs; D039381:RNA Cap-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; C114090:SNUPN protein, human; D006151:Guanosine; D011755:Pyrophosphatases; C005692:triphosphoric acid