title: Parcs/Gpn3 is required for the nuclear accumulation of RNA polymerase II.
abstract: Parcs/Gpn3 is a putative GTPase that is conserved in eukaryotic cells from yeast to humans, suggesting that it plays a fundamental, but still unknown, cellular function. Suppression of Parcs/Gpn3 expression by RNAi completely blocked cell proliferation in MCF-12A cells and other mammary epithelial cell lines. Unexpectedly, Parcs/Gpn3 knockdown had a more modest effect in the proliferation of the tumorigenic MDA-MB-231 and SK-BR3 cells. RNA polymerase II (RNAP II) co-immunoprecipitated with Parcs/Gpn3. Parcs/Gpn3 depletion caused a reduction in overall RNA synthesis in MCF-12A cells but not in MDA-MB-231 cells, demonstrating a role for Parcs/Gpn3 in transcription, and pointing to a defect in RNA synthesis by RNAP II as the possible cause of halted proliferation. The absence of Parcs/Gpn3 in MCF-12A cells caused a dramatic change in the sub-cellular localization of Rpb1, the largest subunit of RNAP II. As expected, Rpb1 was present only in the nucleus of MCF-12A control cells, whereas in Parcs/Gpn3-depleted MCF-12A cells, Rpb1 was detected exclusively in the cytoplasm. This effect was specific, as histones remained nuclear independently of Parcs/Gpn3. Rpb1 protein levels were markedly increased in Parcs/Gpn3-depleted MCF-12A cells. Interestingly, Rpb1 distribution was only marginally affected after knocking-down Parcs/Gpn3 in MDA-MB-231 cells. In conclusion, we report here, for the first time, that Parcs/Gpn3 plays a critical role in the nuclear accumulation of RNAP II, and we propose that this function explains the relative importance of Parcs/Gpn3 in cell proliferation. Intriguingly, at least some tumorigenic mammary cells have evolved mechanisms that allow them to proliferate in a Parcs/Gpn3-independent manner.
authors.affiliation: Universidad Autonoma de San Luis Potosi, Mexico.
authors.forename: Mónica R
authors.initials: MR
authors.lastname: Calera
authors.forename: Cristina
authors.initials: C
authors.lastname: Zamora-Ramos
authors.forename: Minerva G
authors.initials: MG
authors.lastname: Araiza-Villanueva
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Moreno-Aguilar
authors.forename: Sonia G
authors.initials: SG
authors.lastname: Peña-Gómez
authors.forename: Fabiola
authors.initials: F
authors.lastname: Castellanos-Terán
authors.forename: Angélica Y
authors.initials: AY
authors.lastname: Robledo-Rivera
authors.forename: Roberto
authors.initials: R
authors.lastname: Sánchez-Olea
mesh_terms: D001940:Breast / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D021381:Protein Transport / Q000235:genetics; D034622:RNA Interference / Q000502:physiology; D012319:RNA Polymerase II / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015533:Transcriptional Activation / Q000187:drug effects / Q000235:genetics
chemical_list: D020558:GTP Phosphohydrolases; D012319:RNA Polymerase II; D034741:RNA, Small Interfering; C562157:GPN3 protein, human