Poster abstracts
Poster number 73 submitted by Laura Kirby
Trypanosoma brucei utilizes dual-coding genes through RNA editing
Laura Kirby (Microbiology and Molecular Genetics, Michigan State University), Yanni Sun (Computer Science and Engineering, Michigan State University), Donna Koslowsky (Microbiology and Molecular Genetics, Michigan State University)
Abstract:
Trypanosoma brucei is a disease causing parasite that lives in mammalian hosts and is transmitted by the bite of a tsetse fly. This salivarian trypanosome is exclusively extracellular in the vertebrate host and can continuously replicate within the bloodstream for months, escaping the host’s immune response by switching surface glycoproteins. During growth in the glucose-rich bloodstream, the mitochondrion is down-regulated and lacks a functional electron transport chain. This unique life cycle leads to two main problems: 1) the lack of selection for genes involved in mitochondrial energy production and 2) repeated population bottlenecks, each time they undergo an antigenic switch. These conditions should lead to the rapid accumulation of mutations in the mitochondrial genes required for survival in the insect vector. In our analyses of the gRNA transcriptome, we have identified alternative terminal gRNAs (the last gRNA in the editing cascade) for the CR3 transcript that generate transcripts using different open reading frames. Surprisingly, the alternative reading frame is 9 amino acids longer than the previously identified ORF. Subsequent analyses of the pan-edited mitochondrial genes indicate that several contain extended dual ORFs, and thus could be dual-coding. We hypothesize that RNA editing is a unique mechanism that can be used to gain access to multiple ORFs, and that the overlapping of genetic information helps combat deleterious genetic drift that would occur during growth under non-selective conditions. Using Illumina deep sequencing, we have identified alternative forms of CR3 and ND3 which align their start codons with two different ORFs, and we have identified the alternative gRNAs that direct these edits.
Keywords: Dual-coding genes, RNA-editing