title: Functional role of RNA polymerase II and P70 S6 kinase in KCl withdrawal-induced cerebellar granule neuron apoptosis.
abstract: KCl withdrawal-induced apoptosis in cerebellar granule neurons is associated with aberrant cell cycle activation, and treatment with cyclin-dependent kinase (Cdk) inhibitors protects cells from undergoing apoptosis. Because the Cdk inhibitor flavopiridol is known to inhibit RNA polymerase II (Pol II)-dependent transcription elongation by inhibiting the positive transcription elongation factor b (P-TEFb, a complex of CDK9 and cyclin T), we examined whether inhibition of RNA Pol II protects neurons from apoptosis. Treatment of neurons with 5, 6-dichloro-1-β-D-ribobenzimidazole (DRB), an RNA Pol II-dependent transcription elongation inhibitor, and flavopiridol inhibited phosphorylation and activation of Pol II and protected neurons from undergoing apoptosis. In addition to Pol II, neurons subjected to KCl withdrawal showed increased phosphorylation and activation of p70 S6 kinase, which was inhibited by both DRB and flavopiridol. Immunostaining analysis of the neurons deprived of KCl showed increased nuclear levels of phospho-p70 S6 kinase, and neurons protected with DRB and flavopiridol showed accumulation of the kinase into large spliceosome assembly factor-positive speckle domains within the nuclei. The formation of these foci corresponded with cell survival, and removal of the inhibitors resulted in dispersal of the speckles into smaller foci with subsequent apoptosis induction. Because p70 S6 kinase is known to induce translation of mRNAs containing a 5'-terminal oligopyrimidine tract, our data suggest that transcription and translation of this subset of mRNAs may contribute to KCl withdrawal-induced apoptosis in neurons.
authors.affiliation: From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and jpadmana@health.usf.edu.
authors.forename: Jaya
authors.initials: J
authors.lastname: Padmanabhan
authors.affiliation: the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
authors.forename: Kristy R
authors.initials: KR
authors.lastname: Brown
authors.affiliation: From the Department of Molecular Medicine, University of South Florida Health Byrd Alzheimer's Institute, University of South Florida, Tampa, Florida 33613 and.
authors.forename: Amelia
authors.initials: A
authors.lastname: Padilla
authors.affiliation: the Department of Pathology and Cell Biology, Taub Center for Alzheimer's Disease, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Shelanski
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D007150:Immunohistochemistry; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D011189:Potassium Chloride / Q000378:metabolism / Q000494:pharmacology; D012319:RNA Polymerase II / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism*; D061805:Transcription Elongation, Genetic / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D010880:Piperidines; C077990:alvocidib; D004004:Dichlororibofuranosylbenzimidazole; D011189:Potassium Chloride; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II
keywords: Apoptosis; Cyclin-dependent Kinase (CDK); Neuron; RNA Polymerase II; S6 Kinase; Transcription; Translation