The C-termini of UNC-75, ASD-1, and FOX-1 are the evolutionarily conserved nuclear localization signals.

<p>(<i>A</i>) Amino acid sequence alignment of the C-terminal ends of the CELF family proteins and the putative PY-NLSs from the related proteins <i>C. elegans</i> EXC-7, HRPF-1, human hnRNP F, hnRNP H1 and hnRNP H2 (left), human hnRNP A1, hnRNP D and TAP and the C-terminal ends of the RBFOX family proteins human RBFOX1, RBFOX2, mouse RBFOX3, <i>Drosophila</i> A2bp1, <i>C. elegans</i> ASD-1 and FOX-1 (right). The consensus sequences of the PY-NLS are indicated. The amino acid residues that match the consensus are shaded in yellow or orange. φ, hydrophobic residues. The underlines in the UNC-75 sequence indicate residues substituted with alanine in UNC-75(AAA) used in (<i>C</i>). The underlines in the ASD-1 and FOX-1 sequences indicate residues deleted in the truncated constructs used in (<i>E</i>) and (<i>G</i>), respectively. (<i>B</i>, <i>C</i>) Fluorescence images of the HeLa cells transfected with full-length UNC-75 (<i>B</i>) and UNC-75(AAA) (<i>C</i>) stained with anti-UNC-75 (left panels) and Hoechst 33258 (right panels). (<i>D</i>–<i>G</i>) Confocal images of the HeLa cells transfected with HA-tagged full-length ASD-1 (<i>D</i>), ASD-1(1–388) (<i>E</i>), full-length FOX-1 (<i>F</i>) and FOX-1(1–408) (<i>G</i>) stained with anti-ASD-1 (<i>D</i> and <i>E</i>, left panels) or anti-FOX-1 (<i>F</i> and <i>G</i>, left panels) and TO-PRO3 (right panels). Scale bar, 50 µm.