Poster abstracts
Poster number 42 submitted by Claire Smathers
Exploring splicing and retrotransposition in a mobile group IIC intron
Claire Smathers (Biochemistry, West Virginia University)
Abstract:
Group II introns are ribozymes that are the expected ancestors of both the spliceosome and non-long terminal repeat retroelements, offering a streamlined system to mechanistically examine both splicing and retrotransposition. These introns are divided into three structural families: IIA, IIB, and IIC. In group IIA and IIB introns, the 5’ splice site is decoded by base-pairing interactions between the intron and exon. In contrast, group IIC introns use a combination of short intron-exon base pairing along with a structured rho-independent terminator stem to achieve 5’ exon definition. Group IIC introns have reduced RNA secondary structure complexity compared to their organellar counterparts, and use an unusual hydrolytic splicing pathway in vitro. Here we show that addition of an intron-encoded protein (IEP) switches the self-splicing activity from a hydrolytic to a branched lariat forming reaction. This reaction produces RNPs capable of mobility reactions into DNA targets. We examined this DNA mobility reaction using a novel fluorescent retrohoming assay. We further explored the mechanisms of splicing and retrohoming by utilizing mutant intron RNA, IEP, and altered DNA substrates. Understanding the biochemistry of group IIC intron splicing and mobility will lead to valuable structural and mechanistic insight into how splicing is regulated, and assist our efforts to determine structures of the intron and RNP complex through X-ray crystallography.
Keywords: intron, retroelement, splicing