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

摘要

Primordial germ cells (PGC) are the precursors of germline stem cells. In Drosophila, PGC specification is thought to require transcriptional quiescence and three genes, (), (), and germ cell less () function to downregulate Pol II transcription. While it is not understood how or represses transcription, 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 are a critical regulatory target of . We show that a substantial fraction of the PGCs in embryos have greatly reduced levels of Nos protein and exhibit phenotypes characteristic of PGCs. Lastly, restoring germ cell–specific expression of Nos is sufficient to ameliorate the phenotype.