title: Highly diverged U4 and U6 small nuclear RNAs required for splicing rare AT-AC introns.
abstract: Removal of a rare class of metazoan precursor messenger RNA introns with AU-AC at their termini is catalyzed by a spliceosome that contains U11, U12, and U5 small nuclear ribonucleoproteins. Two previously unidentified, low-abundance human small nuclear RNAs (snRNAs), U4atac and U6atac, were characterized as associated with the AT-AC spliceosome and necessary for AT-AC intron splicing. The excision of AT-AC introns therefore requires four snRNAs not found in the major spliceosome. With the use of psoralen crosslinking, a U6atac interaction with U12 was identified that is similar to a U6-U2 helix believed to contribute to the spliceosomal active center. The conservation of only limited U6atac sequences in the neighborhood of this interaction and the potential of U6atac to base pair with the 5' splice site consensus for AT-AC introns provide support for current models of the core of the spliceosome.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, Howard Hughes Medical Institute, New Haven, CT 06536-0812, USA.
authors.forename: W Y
authors.initials: WY
authors.lastname: Tarn
authors.forename: J A
authors.initials: JA
authors.lastname: Steitz
mesh_terms: D001482:Base Composition; D001483:Base Sequence; D017124:Conserved Sequence; D003432:Cross-Linking Reagents; D005091:Exons; D011564:Furocoumarins; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear / Q000378:metabolism*; D017381:Spliceosomes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D011564:Furocoumarins; D012322:RNA Precursors; D012342:RNA, Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C098762:U11 small nuclear ribonucleoprotein, human; C552126:U11-U12 small nuclear ribonucleoprotein