A dimeric SINE discovered in shrew mole is structurally similar to primate Alu

Urop represents a remarkable case of convergent evolution, independently generating an Alu-like dimeric SINE in a distantly related mammal. Its independent origin from 7SL RNA, parallel structural trajectory (monomer → dimer via identical deletion boundaries), and suppression of tRNA-derived SINEs mirror the evolutionary history of primate Alu. The abundance of long intact poly(A) tails in Urop_c suggests unique biochemical controls on tail dynamics and hint at continued retropositional activity. These findings underscore the exceptional evolutionary potential of rare, large-scale deletions within 7SL RNA as a SINE progenitor and raises new questions about poly(A) tail regulation and SINE family dynamics.