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A spontaneous duplication in U6 spliceosomal RNA uncouples the early and late functions of the ACAGA element in vivo.
RNA. 1996 Sep; 2(9):879-94.RNA

Abstract

U6 RNA enters the spliceosome base paired with U4 RNA, but dissociates from U4 RNA before the catalytic steps of splicing. We have identified a cold-sensitive lethal mutation in U4 RNA (U4-cs1) that blocks the splicing pathway after U4/U6 complex formation, but before the first catalytic step of splicing. Remarkably, selection for suppressors of the cold-sensitive growth of the U4-cs1 strain yielded a tandem duplication of the highly conserved ACAGA sequence of U6 RNA (U6-Dup). The ACAGA sequence plays an essential role in spliceosome assembly and in the second catalytic step of pre-mRNA splicing; one or both of these roles involves direct base pairing to the pre-mRNA 5' splice site. In a U4-cs1/U6-Dup double-mutant strain grown at low temperature, the upstream ACAGA sequence of U6 RNA is required for suppression of the U4 mutation, whereas the downstream ACAGA sequence is required for other essential functions. Based on the sequence requirements for function of the upstream ACAGA element of U6-Dup, we propose that it pairs with the pre-mRNA 5' splice site during incorporation of the U4/U6 complex into the spliceosome and that the subsequent dissociation of U4 RNA exposes the downstream ACAGA sequence, which functions in the catalytic steps. The properties of this mutant U4/U6 complex provide compelling in vivo evidence that U6 RNA normally base pairs with the 5' splice site before disruption of its pairing with U4 RNA.

Authors+Show Affiliations

Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison 53706-1532, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

8809015

Citation

Li, Z, and D A. Brow. "A Spontaneous Duplication in U6 Spliceosomal RNA Uncouples the Early and Late Functions of the ACAGA Element in Vivo." RNA (New York, N.Y.), vol. 2, no. 9, 1996, pp. 879-94.
Li Z, Brow DA. A spontaneous duplication in U6 spliceosomal RNA uncouples the early and late functions of the ACAGA element in vivo. RNA. 1996;2(9):879-94.
Li, Z., & Brow, D. A. (1996). A spontaneous duplication in U6 spliceosomal RNA uncouples the early and late functions of the ACAGA element in vivo. RNA (New York, N.Y.), 2(9), 879-94.
Li Z, Brow DA. A Spontaneous Duplication in U6 Spliceosomal RNA Uncouples the Early and Late Functions of the ACAGA Element in Vivo. RNA. 1996;2(9):879-94. PubMed PMID: 8809015.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - A spontaneous duplication in U6 spliceosomal RNA uncouples the early and late functions of the ACAGA element in vivo. AU - Li,Z, AU - Brow,D A, PY - 1996/9/1/pubmed PY - 1996/9/1/medline PY - 1996/9/1/entrez SP - 879 EP - 94 JF - RNA (New York, N.Y.) JO - RNA VL - 2 IS - 9 N2 - U6 RNA enters the spliceosome base paired with U4 RNA, but dissociates from U4 RNA before the catalytic steps of splicing. We have identified a cold-sensitive lethal mutation in U4 RNA (U4-cs1) that blocks the splicing pathway after U4/U6 complex formation, but before the first catalytic step of splicing. Remarkably, selection for suppressors of the cold-sensitive growth of the U4-cs1 strain yielded a tandem duplication of the highly conserved ACAGA sequence of U6 RNA (U6-Dup). The ACAGA sequence plays an essential role in spliceosome assembly and in the second catalytic step of pre-mRNA splicing; one or both of these roles involves direct base pairing to the pre-mRNA 5' splice site. In a U4-cs1/U6-Dup double-mutant strain grown at low temperature, the upstream ACAGA sequence of U6 RNA is required for suppression of the U4 mutation, whereas the downstream ACAGA sequence is required for other essential functions. Based on the sequence requirements for function of the upstream ACAGA element of U6-Dup, we propose that it pairs with the pre-mRNA 5' splice site during incorporation of the U4/U6 complex into the spliceosome and that the subsequent dissociation of U4 RNA exposes the downstream ACAGA sequence, which functions in the catalytic steps. The properties of this mutant U4/U6 complex provide compelling in vivo evidence that U6 RNA normally base pairs with the 5' splice site before disruption of its pairing with U4 RNA. SN - 1355-8382 UR - https://www.unboundmedicine.com/medline/citation/8809015/A_spontaneous_duplication_in_U6_spliceosomal_RNA_uncouples_the_early_and_late_functions_of_the_ACAGA_element_in_vivo_ L2 - http://www.rnajournal.org/cgi/pmidlookup?view=long&pmid=8809015 DB - PRIME DP - Unbound Medicine ER -