James Brindle | PubMed Health

PubMed2005

Tuning of RNA editing by ADAR is required in Drosophila.

RNA editing increases during development in more than 20 transcripts encoding proteins involved in rapid synaptic neurotransmission in Drosophila central nervous system and muscle. Adar (adenosine deaminase acting on RNA) mutant flies expressing only genome-encoded, unedited isoforms of ion-channel subunits are viable but show severe locomotion defects. The Adar transcript itself is edited in adult wild-type flies to generate an isoform with a serine to glycine substitution close to the ADAR active site. We show that editing restricts ADAR function since the edited isoform of ADAR is less active in vitro and in vivo than the genome-encoded, unedited isoform. Ubiquitous expression in embryos and larvae of an Adar transcript that is resistant to editing is lethal. Expression of this transcript in embryonic muscle is also lethal, with above-normal, adult-like levels of editing at sites in a transcript encoding a muscle voltage-gated calcium channel.

Adenosine Deaminase↗

PubMed2002

Micro-processing events in mRNAs identified by DHPLC analysis.

Post-transcriptional processes such as alternative splicing and RNA editing have a huge impact on the diversity of the proteome. Detecting alternatively spliced transcripts is difficult when they are rare. In addition, edited transcripts often differ from the genomic sequence by only a few nucleotides. Denaturing high performance liquid chromatography (DHPLC) is routinely used for single nucleotide polymorphism detection and we used this method to detect alternatively spliced or edited transcripts. As the sites of RNA editing appear to be conserved within gene families, we investigated whether editing sites are conserved in the murine homologue of the Drosophila cacophony transcript encoding the alpha1 subunit of a voltage-gated calcium channel that is edited at 10 independent positions. Although DHPLC analysis detects RNA editing at as low as 3% in control transcripts, no evidence of RNA editing was found in the analysed murine transcript. However an alternative exon was identified at the 3' end of the mouse Cacna1alpha transcript and an alternative micro-exon encoding only two amino acids (NP) was found in the extracellular loop before the IVS4 helix in the same transcript. In the homologous Drosophila transcript a micro-exon also encoding two amino acids was found at the same position before the IVS4 helix.

Alternative Splicing↗