Protein-free small nuclear RNAs catalyze a two-step splicing reaction.
Pre-mRNA splicing is a crucial step in eukaryotic gene expression and is carried out by a highly complex ribonucleoprotein assembly, the spliceosome. Many fundamental aspects of spliceosomal function, including the identity of catalytic domains, remain unknown. We show that a base-paired complex of U6 and U2 small nuclear RNAs, in the absence of the approximately 200 other spliceosomal components, performs a two-step reaction with two short RNA oligonucleotides as substrates that results in the formation of a linear RNA product containing portions of both oligonucleotides. This reaction, which is chemically identical to splicing, is dependent on and occurs in proximity of sequences known to be critical for splicing in vivo. These results prove that the complex formed by U6 and U2 RNAs is a ribozyme and can potentially carry out RNA-based catalysis in the spliceosome.
Valadkhan
Saba
S
Center for RNA Molecular Biology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA. saba.valadkhan@case.edu
Mohammadi
Afshin
A
Jaladat
Yasaman
Y
Geisler
Sarah
S
D001483:Base Sequence; D055162:Biocatalysis; D004951:Esterification; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000235:genetics; D011506:Proteins / Q000378:metabolism*; D012326:RNA Splicing / Q000235:genetics*; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017381:Spliceosomes / Q000378:metabolism; D013379:Substrate Specificity
D009841:Oligonucleotides; D011506:Proteins; D012342:RNA, Small Nuclear; C405484:U2 small nuclear RNA; C405486:U6 small nuclear RNA