Identification of Factors Critical for SINE Retrotransposition

点击翻译按钮获取中文摘要

Abstract Short INterspersed Elements (SINEs) are mobile genetic elements that are present in all mammalian genomes. Most mammalian SINEs can be subdivided into two general categories: (1) those derived from 7SL signal recognition particle RNA (e.g., human Alu elements); and (2) those derived from transfer RNAs (e.g., canine SINEC_Cf elements). Alu and SINEC_Cf elements have had a major impact on genome evolution and comprise an astounding ~11% and ~15% of human and canine genomic DNA, respectively. The vast majority of SINEs have been rendered immobile by mutational processes; however, some human-specific Alu elements and canine SINEC_Cf elements can mobilize to new genomic locations by a “copy and paste” mechanism termed retrotransposition. To date, greater than 76 independent germline Alu retrotransposition events have been implicated as the cause of human diseases, including cancer. SINEC_Cf retrotransposition events are responsible for various diseases and phenotypic differences in canines. SINEs do not encode proteins; thus, they are classified as `non-autonomous' retrotransposons. Previous studies, including our preliminary data, demonstrate that a protein encoded by an autonomous Long INterspersed Element-1 (LINE-1) retrotransposon (LINE-1 ORF2p) is required for Alu and SINEC_Cf element retrotransposition. We hypothesize that the structure of Alu RNA, and by extension SINEC_Cf RNA, and unidentified host factor(s) allow these RNAs to localize to the ribosome, where they can compete with the LINE-1 poly(A) tail for LINE-1 ORF2p binding to promote their retrotransposition. Here, we propose to use a combination of molecular biological, evolutionary inference, genetic, genomic, and biochemical approaches to: (1) use established RNA secondary structure models, Illumina-based SHAPE-MaP chemical probing, and established cultured cell assays to uncover cis- acting RNA structures and sequences required for human-specific Alu and SINEC_Cf retrotransposition; and (2) exploit differences between HeLa cell isolates that differ in their ability to support Alu and SINEC_Cf retrotransposition to identify host factor(s) critical for SINE retrotransposition. This proposal builds on successful collaborations between the Moran and Kidd laboratories at the University of Michigan and will combine the Moran laboratory's expertise in transposable element and RNA biology with the Kidd laboratory's expertise in computational and statistical genomics and evolutionary biology to elucidate SINE retrotransposition mechanisms.