Fig. 2. The nurf-1 locus is predicted to encode multiple proteins. Each protein shares domains with Drosophila NURF301. Only the isoform containing the HMGA domain is required for antagonism of the synMuv genes. (A) Genomic structures of the nurf-1 isoforms. Exons are indicated by black boxes; 5' and 3' untranslated regions are indicated by white boxes. The predicted translation initiation and termination codons and the polyadenylation sites are indicated. The locations of the two deletion alleles are shown. (B) A representation of the NURF-1 protein and domain structure. (Top) The Drosophila NURF301 protein. (Bottom) The predicted protein products of the nurf-1 gene. An alignment of the predicted functional domains of NURF-1 with those of Drosophila NURF301 is presented in Fig. S3. (C) Reduction of nurf-1a function suppresses the synMuv phenotype of lin-15AB mutants. RNAi of the nurf-1a isoform (pEA147) but not of the nurf-1b, nurf-1c, nurf-1d, nurf-1e isoforms (pEA30) caused suppression of the lin-15AB synMuv phenotype. In addition, deletion of the nurf-1a isoform (n4293) but not of the nurf-1b, nurf-1c, nurf-1d, nurf-1e isoforms (n4295) caused suppression of the lin-15AB synMuv phenotype. M⁺ denotes progeny of heterozygous mutant hermaphrodites, such progeny might retain maternally inherited nurf-1a gene products.