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Hello. I'm Steve Hajduk.
Today's lecture is on RNA editing.
So what exactly is RNA editing?
RNA editing was first described in 1986 by Rob Bennie and coworkers.
In studies on African trypanosomes,
they found that some messenger RNAs differed from
their genes that encoded them by the insertion of nucleotides.
These insertions led to changes in the coding potential for those messenger RNAs.
Since that initial discovery,
RNA editing has been described in a wide range of organisms and
very diverse mechanisms can lead to changes in the RNA transcripts.
RNA editing has only been found in eukaryotes.
In the lecture today, I'll give you a brief overview of some of
the diverse mechanisms which have evolved in eukaryotes to generate edited RNAs.
The bulk of the lecture, however,
will focus on the mechanism, the origin,
and the function of RNA editing in African trypanosomes.
These are the same organisms that Rob Bennie and
coworkers were studying when they first discovered RNA editing.
In the lecture, I'll give you a brief overview of
some more conventional RNA processing reactions,
these are RNA splicing reactions,
and I'll contrast these to the mechanisms used in RNA editing.
Then I'll go through and systematically describe RNA editing in
a number of different organisms including paramyxovirus,
slime molds, plants, mammals and again the kinetoplastids or the trypanosomes.
RNA editing and RNA splicing are superficially quite similar.
The final products are RNA molecules which differ from the genes that encode the RNAs.
And there are some overall similarities: messenger RNAs, tRNAs,
ribosomal RNAs can all be substrates for editing and for splicing.
Alternative mRNA splicing and editing generate protein diversity.
Splicing and editing are both developmentally regulated processes.
However, there's a number of very fundamental differences.
First, splicing removes RNA sequences encoded by the gene.
Editing changes or adds the information encoded by the gene.
Splicing of an RNA is often RNA catalyzed whereas,
RNA editing is always protein catalyzed.
The first form of RNA splicing described was a group I intron.