title: Trimethylguanosine nucleoside inhibits cross-linking between Snurportin 1 and m3G-CAPPED U1 snRNA.
abstract: Macromolecular nuclear import is an energy-and signal-dependent process. The best characterized type of nuclear import consists of proteins carrying the classical NLS that is mediated by the heterodimeric receptor importin alpha/beta. Spliceosomal snRNPs U1, U2, U4, and U5 nuclear import depend both on the 5' terminal m3G (trimethylguanosine) cap structure of the U snRNA and the Sm core domain. Snurportin 1 recognizes the m3G-cap structure of m3G-capped U snRNPs. In this report, we show how a synthesized trimethylguanosine nucleoside affects the binding of Snurportin 1 to m3G-capped U1 snRNA in a UV-cross-linking assay. The data indicated that TMG nucleoside is an essential component required in the recognition by Snurportin 1, thus suggesting that interaction of Snurportin 1 with U1 snRNA is not strictly dependent on the presence of the whole cap structure, but rather on the presence of the TMG nucleoside structure. These results indicate that the free nucleoside TMG could be a candidate to be an inhibitor of the interaction between Snurportin 1 and U snRNAs. We also show the behavior of free TMG nucleoside in in vitro U snRNPs nuclear import.
authors.affiliation: Institut de Biología Molecular de Barcelona, CSIC (IBMB-CSIC), Barcelona. daniabahia@hotmail.com
authors.forename: Diana
authors.initials: D
authors.lastname: Bahia
authors.forename: Anna
authors.initials: A
authors.lastname: Aviñó
authors.forename: Edward
authors.initials: E
authors.lastname: Darzynkiewicz
authors.forename: Ramon
authors.initials: R
authors.lastname: Eritja
authors.forename: Montserrat
authors.initials: M
authors.lastname: Bach-Elias
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D006151:Guanosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D009705:Nucleosides / Q000737:chemistry / Q000494:pharmacology*; D039381:RNA Cap-Binding Proteins / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D012315:RNA Caps / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D012342:RNA, Small Nuclear / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D009705:Nucleosides; D039381:RNA Cap-Binding Proteins; D012315:RNA Caps; D012342:RNA, Small Nuclear; D018160:Receptors, Cytoplasmic and Nuclear; C114090:SNUPN protein, human; C405483:U1 small nuclear RNA; D006151:Guanosine; C017778:N(2),N(2),7-trimethylguanosine