Lc. Shaw et As. Lewin, PROTEIN-INDUCED FOLDING OF A GROUP-I INTRON IN CYTOCHROME-B PRE-MESSENGER-RNA, The Journal of biological chemistry, 270(37), 1995, pp. 21552-21562
Some group I introns have been shown to be self-splicing in vitro, but
perhaps all require proteins for splicing in vivo, Sequence differenc
es affect the stability of secondary structures and may explain why so
me group I introns function efficiently without protein cofactors whil
e others require them. The terminal intron of the cytochrome b pre-mRN
A from yeast mitochondria needs a nucleus encoded protein for splicing
, even though it splices autocatalytically in high salt in vitro. This
system has the advantage that the protein is specific for this intron
, and yet the structure of the catalytically active RNA can be studied
in its absence, We have modified the intron by chemical and enzymatic
treatment in the presence and absence of the protein to determine the
impact of the protein on the secondary and tertiary structures of the
intron, We found protein-induced formation of secondary and tertiary
structures within the intron, and the same structures also form in hig
h salt autocatalytic conditions, We have also studied UV cross-links t
o determine those bases of the intron that interact directly with the
protein and found that the protein contacts the intron most intimately
at the structures denoted P1, L2, P4, and P6a.