Evolutionary analysis of the T-Ag protein. (a) Diagram of the SV40 T-Ag protein (708 aa). The J-domain, with embedded HPDKGG hexapeptide, Rb binding motif, nuclear localization signal (NLS), and helicase domains are indicated. The helicase domain is divided into a zinc (Zn) domain and the ATPase. (b) Maximum likelihood phylogenetic tree of the T-Ag protein. Trees were rooted using SV40, and the remaining (n=114) amniote PyVs were removed to improve visualization (complete trees available in Fig. S2). Nodes with bootstrap support less than 70 % were collapsed. Diagrams to the right of the tree show the individual domains in T-Ag DnaJ (grey), the HPDKGG hexapeptide (black diamond). Origin binding domain (blue) and helicase domain (purple). English host names are used to refer to the associated fish PyVs. (c) Homology models of the different PyV DnaJ domains homology modelled on the murine PyV DnaJ domain (1FAF [42]). Models for SV40 (purple), the guitarfish (blue), marbled (green) and Japanese (yellow) eel viruses were visualized and analysed using Chimera version 1.11.2 [43]. (d) Merged overlay of the models shown in (c). The black arrow head points towards the conserved HPDKGG hexapeptide.