Fig. 1. The hephaestus locus. (A) Five heph alleles map to a single, complex transcription unit predicted to encode an RNA-binding protein with four RNA-recognition motifs (RRM1-4). Three P-element alleles (heph⁰³⁴²⁹, heph^j11B9 and heph²) map to heph introns and two EMS-induced alleles (heph^e1 and heph^e2) alter conserved RNA-binding domains. Alternative splicing produces predicted protein variants: isoforms A and B include a bipartite nuclear localization signal (NLS). Only isoform A includes an N-terminal glutamine-rich domain (Q-rich). (B) The heph protein is highly related to the previously characterized RNA-binding proteins PTB/hnRNPI (human, NM_002819) and Vg1RBP60 (Xenopus, AF091370). Percent amino acid identity is indicated and, in brackets, percent similarity.