Mol. Cell. Biol., 08 1996, 4584-4589, Vol 16, No. 8
GC Frech and L Simpson
An RNA editing-like internal uridine (U) incorporation activity (G. C.
Frech, N. Bakalara, L Simpson, and A. M. Simpson, EMBO J. 14:178-187, 1995)
and a 3'-terminal U addition activity (N. Bakalara, A. M. Simpson, and L.
Simpson, J. Biol. Chem. 264:18679-18686, 1989) have been previously
described by using a mitochondrial extract from Leishmania tarentolae.
Chiral phosphorothioates were used to investigate the stereoconfiguration
requirements and the stereochemical course of these nucleotidyl transfer
reactions. The extract utilizes (SP)-alpha-S-UTP for both 3' and internal U
incorporation into substrate RNA. The internal as well as the 3'
incorporation of (SP)- alpha-S-UTP proceeds via inversion of the
stereoconfiguration. Furthermore, internal U incorporation does not occur
at sites containing thiophosphodiesters of the RP configuration. Our
results are compatible with an enzyme cascade model for this in vitro U
insertion activity involving sequential endonuclease and uridylyl
transferase directly from UTP and RNA ligase steps and are incompatible
with models involving the transfer of U residues from the 3' ends of guide
RNAs.
Copyright © 1996, American Society for Microbiology
Uridine insertion into preedited mRNA by a mitochondrial extract from Leishmania tarentolae: stereochemical evidence for the enzyme cascade model
Howard Hughes Medical Institute, University of California, Los Angeles 90095-1662, USA.
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