Autoantibodies target the RNA binding protein Ro60 in systemic lupus erythematosus (SLE) and Sjögren’s syndrome. However, whether Ro60 and its associated RNAs contribute to disease pathogenesis is unclear. We catalogued the Ro60-associated RNAs in human cell lines and found that among other RNAs, Ro60 bound an RNA motif derived from endogenous Alu retroelements. Alu transcripts were induced by type I interferon and stimulated proinflammatory cytokine secretion by human peripheral blood cells. Ro60 deletion resulted in enhanced expression of Alu RNAs and interferon-regulated genes. Anti-Ro60 positive SLE immune complexes contained Alu RNAs, and Alu transcripts were upregulated in SLE whole blood samples compared to controls. These findings establish a link between the lupus autoantigen Ro60, Alu retroelements and type I interferon.

DINE-1 (Drosophila interspersed element) is the most abundant repetitive sequence in the Drosophila genome derived from transposable elements. It comprises .1% of the Drosophila melanogaster genome (DMG) and is believed to be a relic from an ancient transpositional burst that occurred 5-10 MYA. We performed a genomewide comparison of the abundance, sequence variation, and chromosomal distribution of DINE-1 in D. melanogaster and D. yakuba. Unlike the highly diverged copies in the DMG (pairwise distance 15%), DINE-1's in the Drosophila yakuba genome (DYG) have diverged by only 3.4%. Moreover, the chromosomal distribution of DINE-1 in the two species is very different, with a significant number of euchromatic insertions found only in D. yakuba. We propose that these different patterns are caused by a second transpositional burst of DINE-1's in the D. yakuba genome 1.5 MYA. On the basis of the sequence of these recently transposed copies, we conclude that DINE-1 is likely to be a family of nonautomomous DNA transposons. Analysis of the chromosomal distribution of two age groups of DINE-1's in D. yakuba indicates that (1) there is a negative correlation between recombination rates and the density of DINE-1's and (2) younger copies are more evenly distributed in the chromosome arms, while older copies are mostly located near the centromere regions. Our results fit the predictions of a selection-transposition balance model. Our data on whole-genome comparison of a highly abundant TE among Drosophila sibling species demonstrate the unexpectedly dynamic nature of TE activity in different host genomes.