Maintaining Sufficient Nanos Is a Critical Function for Polar Granule Component in the Specification of Primordial Germ Cells

摘要

pPrimordial germ cells (PGC) are the precursors of germline stem cells. In iDrosophila/i, PGC specification is thought to require transcriptional quiescence and three genes, ipolar granule component/i (ipgc/i), inanos/i (inos/i), and igerm cell less/i (igcl/i) function to downregulate Pol II transcription. While it is not understood how inos/i or igcl/i represses transcription, ipgc/i does so by inhibiting the transcription elongation factor b (P-TEFb), which is responsible for phosphorylating Ser2 residues in the heptad repeat of the C-terminal domain (CTD) of the largest Pol II subunit. In the studies reported here, we demonstrate that inos/i are a critical regulatory target of ipgc/i. We show that a substantial fraction of the PGCs in ipgc/i embryos have greatly reduced levels of Nos protein and exhibit phenotypes characteristic of inos/i PGCs. Lastly, restoring germ cella€“specific expression of Nos is sufficient to ameliorate the ipgc/i phenotype./p