THE DROSOPHILA RIBOSOMAL-PROTEIN L14-ENCODING GENE, IDENTIFIED BY A NOVEL MINUTE MUTATION IN A DENSE CLUSTER OF PREVIOUSLY UNDESCRIBED GENES IN CYTOGENETIC REGION 66D

The Minute phenotype results from mutations at > 50 loci scattered thr oughout the genome of Drosophila. Common traits of the Minute phenotyp e are short and thin bristles, slow development, and recessive lethali ty. Here, we report a novel P-element induced Minute mutation, P{lacW} M(3)66D(1), that maps to region 66D on chromosome 3L. Flies heterozygo us for P{lacW}M(3)66D(1) have a strong Minute phenotype. Molecular cha racterisation of the chromosomal region revealed three previously unde scribed Drosophila genes clustered within a 5-kb genomic fragment. Two of the genes have significant sequence homology to genes for the mamm alian ribosomal proteins L14 and RD, respectively, and share a joint 2 40-bp promoter region harbouring the P-element insert. Quantitative No rthern blot analyses showed the mutation to affect RPL14 mRNA levels o nly. Interestingly, the reduction in abundance of RPL14 mRNA is not co nstitutive, indicating that the promoter function abolished by the ins erted P-element is utilised with different efficiencies in different d evelopmental situations. Remobilisation of the P element produced wild -type flies with normal levels of RPL14 mRNA, demonstrating that the m utant phenotype is caused by the insertion. P{lacW}M(3)66D(1) joins a growing list of Minute mutations associated with ribosomal protein-hap loinsufficiency.