U2-U6 RNA folding reveals a group II intron-like domain and a four-helix junction.
Intron removal in nuclear precursor mRNA is catalyzed through two transesterification reactions by a multi-megaDalton ribonucleoprotein machine called the spliceosome. A complex between U2 and U6 small nuclear RNAs is a core component of the spliceosome. Here we present an NMR structural analysis of a protein-free U2-U6 complex from Saccharomyces cerevisiae. The observed folding of the U2-U6 complex is a four-helix junction, in which the catalytically important AGC triad base-pairs only within U6 and not with U2. The base-pairing of the AGC triad extends the U6 intramolecular stem-loop (U6 ISL), and the NMR structure of this extended U6 ISL reveals structural similarities with domain 5 of group II self-splicing introns. The observed conformation of the four-helix junction could be relevant to the first, but not the second, step of splicing and may help to position the U6 ISL adjacent to the 5' splice site.
Sashital
Dipali G
DG
Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, Wisconsin 53706, USA.
Cornilescu
Gabriel
G
McManus
C Joel
CJ
Brow
David A
DA
Butcher
Samuel E
SE
D001483:Base Sequence; D001665:Binding Sites; D007438:Introns; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D017381:Spliceosomes / Q000737:chemistry / Q000378:metabolism
D012342:RNA, Small Nuclear; C405484:U2 small nuclear RNA; C405486:U6 small nuclear RNA