Retrotransposon profiling of RNA polymerase III initiation sites
- Xiaojie Qi1,
- Kenneth Daily1,
- Kim Nguyen1,
- Haoyi Wang2,
- David Mayhew2,
- Paul Rigor1,
- Sholeh Forouzan1,
- Mark Johnston2,
- Rob David Mitra2,
- Pierre Baldi1 and
- Suzanne Sandmeyer1,3
- ↵* Corresponding author; email: sbsandme{at}uci.edu
Abstract
Although retroviruses are relatively promiscuous in choice of integration sites, retrotransposons can display marked integration specificity. In yeast and slime mold some retrotransposons are associated with tRNA genes (tDNAs). In the Saccharomyces cerevisiae genome the long terminal repeat retrotransposon Ty3 is found at RNA polymerase III (Pol III) transcription start sites of tDNAs. Ty1, 2, and 4 elements also cluster in the upstream regions of these genes. In order to determine the extent to which other Pol III-transcribed genes serve as genomic targets for Ty3, a set of 10,000 Ty3 genomic retrotranspositions were mapped using high throughput DNA sequencing. Integrations occurred at all known tDNAs, two tDNA relics (iYGR033c and ZOD1), and six non-tDNA, Pol III-transcribed types of genes (RDN5, SNR6, SNR52, RPR1, RNA170, and SCR1). Previous work in vitro demonstrated that the Pol III transcription factor (TF) IIIB is important for Ty3 targeting. However, seven loci that bind the TFIIIB loader, TFIIIC, were not targeted, underscoring the unexplained absence of TFIIIB at those sites. Ty3 integrations also occurred in two open reading frames not previously associated with Pol III transcription, suggesting the existence of a small number of additional sites in the yeast genome that interact with Pol III transcription complexes.
- Received August 27, 2011.
- Accepted January 25, 2012.
- Copyright © 2012, Cold Spring Harbor Laboratory Press
