Repositioning of the reaction intermediate within the catalytic center of the spliceosome.
Conformational change within the spliceosome is required between the first catalytic step of pre-mRNA splicing, when the branch site attacks the 5' splice site (SS), and the second step, when the 5' exon attacks the 3'SS. Little is known, however, about repositioning of the reaction substrates during this transition. Whereas the 5'SS is positioned for the first step by pairing with the invariant U6 snRNA-ACAGAG site, we demonstrate that this pairing interaction must be disrupted to allow transition to the second step. We propose that removal of the branch structure from the catalytic center is in competition with binding of the 3'SS substrate for the second step. Changes in the relative occupancy of first and second step substrates at the catalytic center alter efficiency of the two steps of splicing, allowing use of suboptimal intron sequences and thereby altering substrate selectivity.
Konarska
Maria M
MM
The Rockefeller University, New York, New York 10021, USA. konarsk@mail.rockefeller.edu
Vilardell
Josep
J
Query
Charles C
CC
D001483:Base Sequence; D020134:Catalytic Domain; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D017381:Spliceosomes / Q000737:chemistry / Q000378:metabolism
D012342:RNA, Small Nuclear; C405486:U6 small nuclear RNA