MSCV integrations promote the expression of Evi1 and Prdm16 isoforms lacking the PR domain. (A) Mouse Mds1 locus and partial Evi1 locus with MSCV integrations are shown in the top panel. Mds1 and Evi1 exons are depicted as blue and yellow boxes, respectively. Red triangles indicate the location and orientation of integrated MSCV. Asterisks indicate translational start sites. The bottom panel depicts the generation of the Mds1-Evi1 fusion transcript and shows the location of the PR domain. (B) Mouse Prdm16 locus (partial) with MSCV integrations and the transcript encoding the long Prdm16 isoform containing the PR domain. Exons are depicted as yellow boxes. Translational start sites for the long and short isoforms are indicated by asterisks. (C) The nature of the fusion transcript between MSCV and Prdm16 exon 2 is shown. SD indicates splice donor in MSCV.