DROSOPHILA RPS3A, A NOVEL MINUTE GENE SITUATED BETWEEN THE SEGMENT POLARITY GENES CUBITUS INTERRUPTUS AND DTCF

Genetic analysis of the small chromosome 4 of Drosophila has been hamp ered by the virtual lack of recombination, The segment polarity gene c ubitus interruptus (ci) maps to the most intensively studied locus on this chromosome. Up to four complementation groups have been found to be associated with ci. We and others have recently characterized a sec ond segment polarity gene, dTCF or pan, 12 kb upstream of ci, in a hea d-to-head configuration, During the course of these studies we identif ied a transcription unit in the intergenic region. We report here the cloning of cDNAs from this transcription unit, which encode the Drosop hila homologue of the human ribosomal protein S3a (RpS3a), The RpS3a g ene is expressed ubiquitously and throughout development. A Minute all ele, M(4)101, linked tightly to ci, was found to harbour an integratio n of a Doc retroposon in the promotor region of RpS3a, Thus, like othe r Minute loci, M(4)101 encodes a component of the protein synthesis ma chinery. These data further unravel the complex genetics surrounding t he ci and dTCF loci.