Archive for January, 2009
Characterization of human A-to-I RNA editing recoding targets
We recently identified new A-to-I RNA recoding events through systematic screening of the human SNP database by a combined bioinformatics and experimental strategy. Here we demonstrate that one additional high-scoring candidate gene in the output list, the GC-rich C1q-related factor precursor (C1qL1), undergoes 14% recoding editing at the predicted site in human brain, further confirming the validity of our screening procedure. C1qL1 is an intracellular protein interacting predominantly with the ER and Golgi and is expressed in all brain tissues. It contains a collagen-like domain in its N-terminal half which may allow homo- or hetero-oligomerization. Its C-terminus is comprised of a globular domain that shares homology to the C1q domain, which in other proteins is crucial for protein-protein interactions (target recognition). The amino acid change introduced by editing in this target might potentially affect its ability to oligomerize and/or the proteolytic processing of the protein.
We are investigating another potential editing target, determined by a similar biocomputational approach, which contains a 90 nucleotide long completely double-stranded region in its predicted secondary structure, suggesting that it should be an excellent substrate for ADARs. Yet, sequence analysis of human brain cDNA did not reveal evidence of in vivo editing. However, when minigene constructs were transfected into HeLa cells, we found that editing occurs at 13 out of 24 adenosines in the exonic part of the double-stranded region. Editing further increases when the intronic sequence between the inverted repeat regions is deleted. We are currently investigating how additional sequence features of SERPINA3 primary transcripts might affect in vivo editing.