Tombola, a tesmin/TSO1-family protein, regulates transcriptional activation in the Drosophila male germline and physically interacts with always early

During male gametogenesis, a developmentally regulated and cell type-specific transcriptional programme is activated in primary spermatocytes to prepare for differentiation of sperm. The Drosophila aly-class meiotic-arrest loci (aly, comr, achilvis and topi) are essential for activation of transcription of many differentiation-specific genes, and several genes important for meiotic cell cycle progression, thus linking meiotic divisions to cellular differentiation during spermatogenesis. Protein interaction studies suggest that the aly-class gene products form a chromatin-associated complex in primary spermatocytes. We identify, clone and characterise a new aly-class meiotic-arrest gene, tombola (tomb), which encodes a testis-specific CXC-domain protein that interacts with Aly. The tomb mutant phenotype is more like that of aly and comr mutants than that of achilvis or topi mutants in terms of target gene profile and chromosome morphology. tomb encodes a chromatin-associated protein required for localisation of Aly and Comr, but not Topi, to chromatin Reciprocally, aly and comr, but not topi or achilvis, are required to maintain the normal localisation of Tomb. tomb and aly might be components of a complex paralogous to the Drosophila dREAM/Myb-MuvB and C. elegans DRM transcriptional regulatory complexes.