Fig. 1. Rfx locus and genetic elements. (A) The organization of the Rfx genomic region on chromosome III, centromere to the left. The four P-element insertions and the two deficiencies described in this study are reported. Two elements (jumu⁶¹⁴², jumu⁶⁴³⁹) are located in the jumu gene. The element of the A143.1F3 line is inserted 5' of Rfx and 5' of the CG17100 gene transcription start site. The S143702 P element is inserted in the jumu gene. The insertion event has generated a deficiency uncovering Rfx and jumu-coding regions. The remaining PlacW element is situated at the deficiency breakpoints. Rfx⁴⁹ is a small deficiency uncovering the first three exons of Rfx created by A143.1F3 mobilization. 4 kb of the A143.1F3 P(lArB) element remain in Rfx⁴⁹ at the deficiency breakpoints. (B) Rfx in situ hybridization of Df(3R)hth/TM2 salivary gland polytene chromosomes. Rfx hybridization (arrow) allows the visualization of the loop on the third chromosome because of a complete deficiency of the 85F to 86C regions on chromosome Df(3R)hth. (C) Alignment of RFX DNA-binding domain from different species. Rfx²⁵³ corresponds to a point mutation changing an absolutely conserved serine to a phenylalanine within the DNA-binding domain. Species abbreviations: H.s., Homo sapiens; M.m., Mus musculus; D.m., Drosophila melanogaster; C.e., Caenorhabditis elegans; S.c., Saccharomyces cerevisiae; S.p., Schizosaccharomyces pombe. (D) Electromobility shift assay with in vitro translated wild-type RFX or RFX²⁵³, and an X box-labeled oligonucleotide. Lane 1, no protein; lanes 2-4, RFX; lanes 5-7, RFX²⁵³; lanes 2,5, no competitor; lanes 3,6, X box oligonucleotide as competitor; lanes 4,7, mutated X box oligonucleotide as competitor; RFX²⁵³ is not able to bind an X box oligonucleotide. The arrowhead indicates the free probe. The bracket indicates RFX-DNA complex.