A 3'-terminal minihelix in the precursor of human spliceosomal U2 small nuclear RNA.
U2 RNA is one of five small nuclear RNAs that participate in the majority of mRNA splicing. In addition to its role in mRNA splicing, the biosynthesis of U2 RNA and three of the other spliceosomal RNAs is itself an intriguing process involving nuclear export followed by 5'-cap hypermethylation, assembly with specific proteins, 3' end processing, and then nuclear import. Previous work has identified sequences near the 3' end of pre-U2 RNA that are required for accurate and efficient processing. In this study, we have investigated the structural basis of U2 RNA 3' end processing by chemical and enzymatic probing methods. Our results demonstrate that the 3' end of pre-U2 RNA is a minihelix with an estimated stabilization free energy of -6.9 kcal/mol. Parallel RNA structure mapping experiments with mutant pre-U2 RNAs revealed that the presence of this 3' minihelix is itself not required for in vitro 3'-processing of pre-U2 RNA, in support of earlier studies implicating internal regions of pre-U2 RNA. Other considerations raise the possibility that this distinctive structural motif at the 3' end of pre-U2 RNA plays a role in the cleavage of the precursor from its longer primary transcript or in its nucleocytoplasmic traffic.
Mougin
Annie
A
Unité Mixte Recherche 7567 CNRS-Université Henri Poincaré Nancy I, Maturation des ARN et Enzymologie Moléculaire, Université H. Poincaré, 54506 Vandoeuvre-les Nancy, France.
Torterotot
Françoise
F
Branlant
Christiane
C
Jacobson
Marty R
MR
Huang
Qian
Q
Pederson
Thoru
T
D001483:Base Sequence; D006801:Humans; D008969:Molecular Sequence Data; D012322:RNA Precursors / Q000737:chemistry*; D012342:RNA, Small Nuclear / Q000096:biosynthesis*; D017381:Spliceosomes / Q000737:chemistry*
D012322:RNA Precursors; D012342:RNA, Small Nuclear; C405484:U2 small nuclear RNA