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Changes in rRNA Transcription Influence Proliferation and Cell Fate Within a Stem Cell Lineage

Science  17 Jan 2014:
Vol. 343, Issue 6168, pp. 298-301
DOI: 10.1126/science.1246384

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Germline Pol I

RNA polymerase I (Pol I)–directed ribosomal RNA (rRNA) transcription has been extensively studied in mammalian cell lines and yeast. However, the functional significance of cell-specific regulation of Pol I transcription within developmental contexts in vivo remains unclear. Zhang et al. (p. 298) characterized a Drosophila Pol I regulatory complex and found that germline stem cells (GSCs) of the ovary exhibited increased levels of rRNA transcription relative to their immediate daughter cells. High levels of rRNA expression promoted GSC proliferation, with attenuation of Pol I activity showing effects during early germ cell differentiation.

Abstract

Ribosome biogenesis drives cell growth and proliferation, but mechanisms that modulate this process within specific lineages remain poorly understood. Here, we identify a Drosophila RNA polymerase I (Pol I) regulatory complex composed of Under-developed (Udd), TAF1B, and a TAF1C-like factor. Disruption of udd or TAF1B results in reduced ovarian germline stem cell (GSC) proliferation. Female GSCs display high levels of ribosomal RNA (rRNA) transcription, and Udd becomes enriched in GSCs relative to their differentiating daughters. Increasing Pol I transcription delays differentiation, whereas reducing rRNA production induces both morphological changes that accompany multicellular cyst formation and specific decreased expression of the bone morphogenetic protein (BMP) pathway component Mad. These findings demonstrate that modulating rRNA synthesis fosters changes in the cell fate, growth, and proliferation of female Drosophila GSCs and their daughters.

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