title: A UV-induced, Mg(2+)-dependent crosslink traps an active form of domain 3 of a self-splicing group II intron.
abstract: In vitro irradiation of a15 gamma group II intron RNA with low doses of 254 nm UV light induces a single major crosslink. This crosslink was mapped within the domain 3 substructure of this RNA and one of the participating nucleotides was identified. When an RNA containing only the domain 3 substructure is irradiated under the same conditions, an intramolecular crosslink forms between two specific pyrimidines, one of them identical to the nucleotide crosslinked in the full-length intron RNA. In both RNAs, the crosslink is magnesium ion-dependent and photoreversible. A trans assay for domain 3 function was developed and used to find that the crosslinked domain 3 RNA remains highly reactive. This suggests that crosslinking has trapped a functional, Mg(2+)-induced folded state of this group II intron substructure and that this folding is probably independent of the other domains of the intron.
mesh_terms: D001483:Base Sequence; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins / Q000235:genetics*; D007438:Introns; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011743:Pyrimidines / Q000737:chemistry / Q000528:radiation effects; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D012326:RNA Splicing / Q000187:drug effects / Q000528:radiation effects; D012333:RNA, Messenger; D016914:Ribonuclease H / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014466:Ultraviolet Rays; D014764:Viral Proteins / Q000235:genetics*
chemical_list: C070354:Cox protein, Enterobacteria phage P2; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D011743:Pyrimidines; D012333:RNA, Messenger; D014764:Viral Proteins; D012313:RNA; D016914:Ribonuclease H; D008274:Magnesium