Base-pairing interactions involving the 5' and 3'-terminal nucleotides of group II self-splicing introns.
By combining comparative sequence analyses and nucleotide replacements, we show that formation of the active center of group II introns rests in part on two novel long-range base-pairing interactions. (1) The last nucleotide of group II introns forms a solitary Watson-Crick base-pair with one of the nucleotides in the short sequence stretch connecting domains II and III. Formation of this base-pair is rate-limiting for the 3' cleavage and ligation step. (2) Nucleotides 3 and 4 form base-pairs with two consecutive nucleotides in a well-conserved internal loop of domain I. This interaction is involved in both the 5' and 3' cleavage steps. Possible relationships between group II and nuclear pre-mRNA introns are reassessed by taking into account these new pieces of information.
Jacquier
A
A
Institut Pasteur, Département de Biologie Moléculaire, Paris, France.
Michel
F
F
D001435:Bacteriophages / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D005809:Genes, Regulator; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D011061:Poly A / Q000235:genetics*; D012315:RNA Caps / Q000235:genetics*; D012326:RNA Splicing; D016337:RNA, Catalytic; D012335:RNA, Ribosomal / Q000235:genetics*; D013728:Terminator Regions, Genetic
D012315:RNA Caps; D016337:RNA, Catalytic; D012335:RNA, Ribosomal; D011061:Poly A