A protein encoded by a group I intron in Aspergillus nidulans directly assists RNA splicing and is a DNA endonuclease.
Some group I introns self-splice in vitro, but almost all are thought to be assisted by proteins in vivo. Mutational analysis has shown that the splicing of certain group I introns depends upon a maturase protein encoded by the intron itself. However the effect of a protein on splicing can be indirect. We now provide evidence that a mitochondrial intron-encoded protein from Aspergillus nidulans directly facilitates splicing in vitro. This demonstrates that a maturase is an RNA splicing protein. The protein-assisted reaction is as fast as that of any other known group I intron. Interestingly the protein is also a DNA endonuclease, an activity required for intron mobilization. Mobile elements frequently encode proteins that promote their propagation. Intron-encoded proteins that also assist RNA splicing would facilitate both the transposition and horizontal transmission of introns.
Ho
Y
Y
Department of Biology, Temple University, Philadelphia, PA 19122, USA.
Kim
S J
SJ
Waring
R B
RB
D001233:Aspergillus nidulans / Q000235:genetics* / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000235:genetics* / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D007438:Introns / Q000235:genetics; D012326:RNA Splicing; D012331:RNA, Fungal
D005656:Fungal Proteins; D012331:RNA, Fungal; D003850:Deoxyribonuclease I