Ancestral reconstruction reveals a stabilization of RELA motifs during MER81 evolution. Modern human together with 10 related mammalian species were selected to reconstruct a series of ancestral genomes based on multiple sequence alignments. (A) Phylogenetic tree of the 11 selected species to reconstruct ancestral genomes. Each node in the tree represents a reconstructed genome of the corresponding common ancestor. (B) The number of MER81 copies in each human ancestor genome. Gray and orange represent total numbers and copies containing RELA motifs, respectively. (C) RELA motif change in MER81 along human evolution. The percentage of MER81 proportion containing RELA motifs is shown as a function of the estimated evolutionary age of each node/common ancestor. A simulation of MER81 sequence change based on nucleotide substitution is shown in gray. (D) The distribution of RELA motifs in MER81 instances in all human ancestors. (E) Schematic of a MER81 co-option model during human evolution. Created in BioRender (https://www.biorender.com).
