The Bic-C Family of Developmental Translational Regulators

Figure 1

(a) Alignment of Bic-C sequences from 11 Drosophila species. Clustal W [1, 2] was used to align sequences extracted from FlyBase. Amino acid (aa) color coding is from Clustal W: red, small aliphatic, hydrophobic, and aromatics; blue, acidic; magenta, basic; green, hydroxyl, sulphydryl, amine, and glycine; grey, unusual aa. Symbols for aa conservation are from Clustal W: (asterisk *): positions with a single, fully conserved residue. (Colon  :): conservation between groups of strongly similar properties scoring >0.5 in the Gonnet PAM 250 matrix. (Period  .): conservation between groups of weakly similar properties scoring ≤0.5 in the Gonnet PAM 250 matrix. All three D. melanogaster Bic-C isoforms are shown (PA, PB, PD). The two canonical (KH) and three noncanonical (KH-like) KH RNA-binding modules are indicated (arrows, top). Domain assignment is as in [3] except for the fourth KH-related motif and the SAM domains, that are labelled according to the Pfam database [4]. A conserved, potentially phosphorylated, tyrosine is also indicated (arrowhead, top). Divergence occurs in regions of low complexity in the encoding DNA. Relative to the numbering of the Drosophila sequence: insertion at 555, variable length of the serine stretches around aa 623, and between aa 647–658 in the serine-glycine rich region. Further, after aa 715 there seems to be insertions of glutamine stretches of various lengths in D. mojavensis, D. virilise, and D. grimshawi. Finally, D. ananassae shows a short insertion at aa 770. The D. virilise, sequence results truncated. A TBLASTn search with the C-terminal region of Bic-C from D. melanogaster reveals many ESTs with similarity to the D. melanogaster sequence, suggesting a possible misannotation (not shown). Another region of possible sequencing misannotation in the D. virilis and the D. mojavensis Bic-C is italicized and not in bold type. Note that the Bic-C gene in D. melanogaster has nine mapped introns [5], and there is the possibility that the sequence was misannotated with this respect. (b) Block structure of the D. melanogaster Bic-C highlighting the protein motifs described in the text.