Kurze Promotoren und Translationskontrollelemente steuern die Expression von Don Juan, Don Juan-Like und Min, wobei Don Juan und Don Juan-Like vermutlich funktionell redundant in der Spermiogenese von Drosophila melanogaster sind

The testis spcifically expressed gene don juan (dj) and the newly characterised genes don juan-like (dj-like) and min are a cluster on the 3. chromosome of Drosophila melanogaster. The expression of the genes is translationally controlled. The transcripts are expressed premeiotically but the protein is translated in postmeiotic cells only. The Don Juan protein can be detected in mitochondrial derivatives and in the nuclei. don juan and the adjacent gene dj-like are 70 % identical at the nucleotide level and 42 % identical on protein level. It is supposed that the proteins Don juan, Don Juan-Like and Min are involved in the postmeiotic differentiation process of the sperms. Hence an analysis of the don juan-, don juan-like- and min-generegulation and also a functional analysis of the encoded proteins is reasonable. The Myc-DJ-Like fusionprotein was transgenetically expressed in the male germline under the control of the dj-like promoter. By this the fusionprotein could be specifically localized in the flagella of elongated spermatids and in the spermatidnuclei during chromatincondensation. Testing promoter-reportergene-constructs in transgenic flies it was revealed that the expression of don juan-like and min is regulated by short sequences. While only 200 bp upstream of the translation start codon of min are sufficient for the regulation of the min gene, 650 bp upstream of the translation start codon of don juan-like are sufficient for the expression of the gene dj-like. The region mediating the translational repression of the don juan-mRNA was restricted to 35 bp upstream of the ATG in the Leader of the gene. Also 30 bp in the leader of min upstream of the ATG mediate translational repression of min-mRNA. Both translational control regions show no sequence identities. Expression level of the Min protein depends on Boule and the protein Boule is involved in the translational control of the min-mRNA. The ectopic expression of the fusionproteins Myc-DJ and Myc-DJ-Like in eye imaginaldiscs leads to a reduced eye phenotype suggesting a transcriptional repression function. To reveal the function of DJ, DJ-Like and Min a Ethylmethansulfonat (EMS)-mutagenesis was performed. A male sterile dj-, dj-like and min-phenotype was postulated. Two mutagenised flylines showed a male sterile and a semisterile phenotype respectively over a dj-, dj-like and min deficient flyline. A molecular biological analysis of both flylines showed that there are no mutations in these three genes. Using RNAi-technique the don juan gene was silenced posttranscriptionally resulting in no phenotype. So, Don Juan and Don juan-like could be functionally redundant.