Fig. 8: CTD contributes to PC motif selection.

a ZIM-2 R488K mutant showed a moderately reduced binding to chromosome V PC and showed no binding to X chromosome, chromosome II/III, and chromosome I/IV PC DNA. b The sequence similarity alignment of ZF1-2 and CTD from HIM-8, ZIM-1, ZIM-2, and ZIM-3 proteins was generated using the EMBOSS Needle Pairwise Sequence Alignment (PSA) server. c Schematic diagram illustrating the two zinc fingers (ZF1 and ZF2) and the carboxyl-terminal domain (CTD) of the HIM-8 ZF1-2-CTD^ZIM-2 protein. d The substitution of HIM-8 CTD with ZIM-2-CTD (HIM-8 ZF1-2-CTD^ZIM-2) resulted in reduced binding to the X chromosome PC motif and increased affinity for the chromosome V PC motif. e Images of representative meiotic germ cells from the HIM-8_CTD^ZIM-2::GFP::3 × FLAG animals illustrate that the HIM-8 foci have disappeared in most germline cells within this worm strain. Three times were repeated independently with similar results. f The quantification of the germline cell ratio with or without HIM-8 foci in HIM-8_CTD^ZIM-2::GFP::3 × FLAG animals. Here, “n” denotes the number of cells tested. Data are presented as Mean ± SD. A two-sided t-test was performed. Source data are provided as a Source Data file. g The brood size of the indicated animals at 20 °C is displayed, with “n” representing the number of P0 generation animals whose self-progeny was analyzed. Data are presented as Mean ± SD. A two-sided t-test was performed. WT vs N2, p = 0.0770; CTD^ZIM-2 vs N2, p = 0.2616. h The male ratio of self-progeny produced by wild-type N2, HIM-8_WT::GFP::3 × FLAG, and HIM-8_CTD^ZIM-2::GFP::3 × FLAG hermaphrodites is presented as a measure of X chromosome nondisjunction, with “n” representing the number of animals counted. i The model depicts key features of the ZIM/HIM-8 ZF1-2-CTD binding to chromosome PCs.TG sub-sites as registration sites are highlighted in the light blue box. Evolutionary intervening sequences are highlighted in the pink box. The orange curved arrow shows the intervening sequences substitution from the X chromosome to the chromosome V PC motif. The light blue curved arrows indicate the intervening sequence deletion from the X chromosome to chromosome II/III and I/IV PC motif. Potential residues on ZF1-2 and CTD to affect DNA binding are highlighted (red dots). Conserved base-contacting residues are highlighted with light blue dots. Conserved residues type of ZF1 position −4, −8, and −9 and ZF2 position −1, −2, and −5 recognizing bases are shown. Residues at ZF1 positions −8 and −9 are responsible for TG registration sites (black arrows). Source data are provided as a Source Data file.