Regulation der Transkription und Translation von Mst77F und der Protamine und die Funktion der Protamine während der Spermiogenese von Drosophila

Während der Spermatogenese werden aus diploiden Zellen hochspezialisierte, bewegliche, haploide Spermien zur Fertilisation der Eizelle gebildet. Die grundlegenden Merkmale des Prozesses sind dabei zwischen Drosophila und Säugern konserviert. Im Spermatozyten-Stadium der Spermatogenese wird ein h...

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Bibliographic Details
Main Author: Barckmann, Bridlin
Format: Doctoral Thesis
Language:German
Published: Philipps-Universität Marburg 2009
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Table of Contents: During spermatogensis dipolid germ cell are transfered into highly specialised sperm cells. The major features of this process is conserved between Drosophila and mammales. During the spermatocyte stage the cells start a highly specialised transcriptional progamm during which lots of genes are activated the first and only time during development. Additionally all postmeiotic expressed genes are transcribed during this stage, because of a lack of transcription in postmeiotic stages. The mRNA of these Genes has to be translational repressed over their 5´UTR. These translational repressed mRNAs are transcribed with an testis specific paralog TFIID complex including also testis specific TAFs, the tTAFS. Here we could show with anti-sa ChIPs that the expression of Mst77F and protA abd protB is directly dependent on these tTAFs. Where these translational repressed mRNAs are stored in the cell is completly unknown. We established therefor tow systems, the MS2cp/MS2sl-system and the lN/BoxB-system for in vivo localisation of these mRNAs. During sperm formation the chromatin of the spermatids is reorganised. In Drosophila as well as in mammals the histones are exchanged by transition proteins and in an next step by protamines. hte biological reason for this rearrangment is completly unkown. Terefore, we generated a deletion including both protamine genes (prot Delta) and observed that in Drosophila, protamine genes are not haploinsufficient in contrast to those of mice and humans. Moreover, we show that in prot Delta mutants, histone degradation, distribution of DNA breaks and Tpl(94D)-eGFP and Mst77F expression proceed as in wild-type males. Surprisingly, in homozygous prot Delta mutants, males are fertile and sperm are motile, while about 20% of sperm show abnormally shaped nuclei. The latter phenotype can be rescued by supplying protamine-eGFP but not by supplying Mst77F-eGFP. Finally, we demonstrate a 21% increase in X-ray-induced mutation rate of prot Delta sperm. These data support the long-standing hypothesis that the switch from a histone- to protamine-based chromatin protects the paternal genome from mutagens.