Fig. 2. sma-9 encodes a zinc finger transcription factor. (A) The longest conceptual SMA-9 sequence. Mutation sites in wk55 and qc3 alleles are boxed. Seven C₂H₂ zinc finger motifs, in three clusters, are shaded. NLSs are underlined. S/TPXK/R or SPKK motifs are double underlined. ARDs are bold and underlined. The asterisk indicates the site at which the alternative C terminus begins. The alternative C terminus unique in C. elegans is italic and underlined. The predicted N-terminal initiation sequence (predicted exon 1) is italic and bold. (B) Comparison of the SMA-9, Shn, MBP1 and A-CBP1 zinc finger regions. The Cys and His residues of zinc finger motifs are boxed. The identical residues are shaded. (C) Comparison of the SMA-9, Shn and MBP1 zinc finger domains. The SMA-9 first pair of zinc fingers is highly conserved between invertebrates and vertebrates. The SMA-9 triplet appears to have been either eliminated during vertebrate evolution or acquired in worm-fly lineage. The SMA-9 second pair is unique in C. elegans. The Shn first pair is conserved in vertebrate homologs but not in C. elegans.