title: Phosphorylation of histone H1 by P-TEFb is a necessary step in skeletal muscle differentiation.
abstract: Positive transcription elongation factor b (P-TEFb), the complex of Cyclin T1 and CDK9, activates the transcription of many viral and eukaryotic genes at the point of mRNA elongation. The activity of P-TEFb has been implicated in the differentiation of a number of cell types, including skeletal muscle. In order to promote transcription, P-TEFb hyperphosphorylates RNA Pol II, thereby increasing its processivity. Our previous work identified histone H1 as a P-TEFb substrate during HIV-1 and immediate-early transcription. Here, we examine the role of P-TEFb phosphorylation of histone H1 during differentiation, using the myoblast cell line C2C12 as a model for skeletal muscle differentiation. We found that H1 phosphorylation is elevated in differentiating C2C12, and this phosphorylation is sensitive to P-TEFb inhibition. H1 phosphorylation was also necessary for the induction of three muscle marker genes that require P-TEFb for expression. Additionally, ChIP experiments demonstrate that H1 dissociates from muscle differentiation marker genes in C2C12 cells under active P-TEFb conditions. We determine that both P-TEFb activity and H1 phosphorylation are necessary for the full differentiation of C2C12 myoblasts into myotubes.
authors.affiliation: Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School Worcester, Worcester, Massachusetts, USA.
authors.forename: Siobhan K
authors.initials: SK
authors.lastname: O'Brien
authors.forename: Kendall L
authors.initials: KL
authors.lastname: Knight
authors.forename: Tariq M
authors.initials: TM
authors.lastname: Rana
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics*; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology*; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics* / Q000378:metabolism; D014162:Transfection
chemical_list: D006657:Histones; D042925:Positive Transcriptional Elongation Factor B