Abstract
ABSTRACTMale germ cell differentiation proceeds to a large extent in the absence of active gene transcription. In Drosophila, hundreds of genes whose proteins are required during post-meiotic spermatid differentiation (spermiogenesis) are transcribed in primary spermatocytes. Transcription of these genes depends on the sequential action of the testis meiotic arrest complex (tMAC), Mediator complex, and testis-specific TFIID (tTFIID) complex. How the action of these protein complexes is coordinated and which other factors are involved in the regulation of transcription in spermatocytes is not well understood. Here, we show that the bromodomain proteins tBRD-1 and tBRD-2 regulate gene expression in primary spermatocytes and share a subset of target genes. The function of tBRD-1 was essential for the sub-cellular localization of endogenous tBRD-2 but dispensable for its protein stability. Our comparison of different microarray data sets showed that in primary spermatocytes, the expression of a defined number of genes depends on the function of the bromodomain proteins tBRD-1 and tBRD-2, the tMAC component Aly, the Mediator component Med22, and the tTAF Sa.
Highlights
In Drosophila melanogaster and mammals, the post-meiotic phase of spermatogenesis is characterized by extensive morphological cell changes (Rathke et al, 2014)
Expression of testis-specific bromodomain proteins (tBRDs)-1-eGFP reconstitutes proper sub-cellular localization of tBRD-2 in tbrd-1 mutant spermatocytes Recently, we have shown that the tbrd-1 mutant phenotype is rescued by a tbrd-1-eGFP transgene, which contains the tbrd-1 open reading frame together with 531 bp upstream of the translational start fused in frame with eGFP
Transcription of spermiogenesisrelevant genes is based on the cooperation among TATA box binding protein-associated factors (tTAFs), testis meiotic arrest complex (tMAC) components, and Mediator complex components (Beall et al, 2007; Chen et al, 2011; Hiller et al, 2004; Lu and Fuller, 2015)
Summary
In Drosophila melanogaster and mammals, the post-meiotic phase of spermatogenesis (spermiogenesis) is characterized by extensive morphological cell changes (Rathke et al, 2014). Numerous transcripts are synthesized and translationally repressed Recruitment of tTAFs to chromatin requires the coactivator complex Mediator, and localization of Mediator subunits to chromatin depends on tMAC (Lu and Fuller, 2015). Based on these data, it has been suggested that Mediator acts as a key factor in a tTAF- and tMAC-dependent gene regulatory cascade that leads to transcriptional activation of spermiogenesisrelevant genes (Lu and Fuller, 2015)
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