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. 2012 Jun 25;109(28):11246–11251. doi: 10.1073/pnas.1118566109

Fig. 6.

Fig. 6.

Summary of the origin and evolution of the MER20/MER39-derived dPRL enhancer/promoter. TEs MER20, MER39, and MER77 are indicated. Note that MER77 is present at the prolactin locus in all species on this tree, even if not depicted. An arrow indicates that a region has promoter activity; size of arrow indicates strength of promoter. Note that strength of mouse promoter has not been tested but location has been determined; rabbits do not express decidual prolactin, so their MER20/MER39 region is assumed here to lack a promoter (5). Also note that the presence of decidual prolactin transcripts has not been tested in lemurs. Key events are indicated, such as insertion or deletion of TEs, positive selection (pos. sel.), substitutions that changed activity of the promoter (+ subs), evolution of interstitial invasion (+ interst. inv.), and interaction between killer immunoglobulin-like receptor and major histocompatability complex class I antigen HLA-C (+ KIR/HLA-C).