Full-length LINE-1s with functional ORFs are favoured by host-level selection in human genomes

The effects of transposable elements, such as LINE-1, on host fitness are still poorly understood. Our analysis of the site frequency spectrum of LINE-1s and SNPs within LINE1s in human genomes shows that selection coefficients are higher for full-length than for fragment LINE-1s and on full-length LINE-1s, SNPs are significantly depleted on ORFs and non-synonymous sites within ORFs. These results suggest that host-level selection maintains transposition competent LINE-1s.