Fig. 4.

a Transduction of IAP LTR by an L1. A full length L1MdTf element interrupted by an IAP ERV exists in intron 3 of the Akr1c14 gene on chromosome 13. This L1 is the source element responsible for the Lama2^dy-Pas mutation, with the newly inserted sequence polyadenylated in the IAP LTR. Thick orange lines are L1 genomic sequences and thin orange lines represent L1 RNA. The IAP LTRs and internal sequences are in green. Genes and number of exons are not to scale. b B2 insertion causing gene upregulation. The TNF^BPSM1 mutation is a B2 insertion (in yellow) in the 3′ UTR of Tnf, causing Tnf upregulation due to polyadenylation within the B2 which removes the negative regulatory ARE (AU rich element) from the Tnf mRNA. Mice with this mutation have heart disease and arthritis due to overexpression of TNF. B2 is yellow and thicker black boxes are coding sequences