Unusual phylogenetic distribution of the rTS gene. The sequences of the same set of proteins displayed in Fig. 2 were used to generate a neighbor-joining tree using ClustalX. The tree was displayed in TreeView program, while the taxonomic labels of the species were added manually afterward. In addition to the extension of the N-terminus as indicated in Fig. 2, adjustments to the currently annotated exon boundaries for a few rTS genes were necessarily made based on the best match between their genomic sequences and the human rTSγ protein sequence (see detailed modifications in supplemental materials). Bootstrap values that are over 700 (1000 trials) are shown at the nodes.