title: TIS21/BTG2/PC3 and cyclin D1 are key determinants of nuclear diacylglycerol  kinase-zeta-dependent cell cycle arrest.
abstract: In addition to lipid second messengers derived from the plasma membrane, increasing evidence supports the existence of nuclear lipid-dependent signaling networks. Diacylglycerol is a key second messenger, generated at the nuclear level, which is metabolized by diacylglycerol kinases (DGKs). It has been demonstrated that nuclear DGK-zeta negatively regulates cell cycle progression. The aim of this study was to identify key determinants of nuclear DGK-zeta-dependent cell cycle arrest in C2C12 mouse myoblasts. Using DNA microarrays, Real-Time RT-PCR and western blot, we demonstrated that nuclear DGK-zeta downregulated the expression of cyclin D1 and increased the expression of TIS21/BTG2/PC3, a transcriptional regulator of cyclin D1 with a strong anti-proliferative function. Overexpression of TIS21/BTG2/PC3 blocked the cells in G1 phase of the cell cycle and decreased the levels of Ser807/811 phosphorylated retinoblastoma protein, similarly to overexpression of DGK-zeta. Moreover, during myogenic differentiation of C2C12 cells, we showed an increase of TIS21/BTG2/PC3 expression and a decrease in cyclin D1 levels. siRNA downregulation of TIS21/ BTG2/PC3 impaired myogenic differentiation by opposing cell cycle arrest. In summary, these data identify TIS21/BTG2/PC3 and cyclin D1 as downstream effectors of nuclear DGK-zeta and highlight the importance of this DGK isoform in the regulation of myoblast proliferation and differentiation.
authors.affiliation: Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Cell Signalling Laboratory, Università di Bologna, via Irnerio 48, 40126 Bologna, Italy.
authors.forename: Camilla
authors.initials: C
authors.lastname: Evangelisti
authors.forename: Annalisa
authors.initials: A
authors.lastname: Astolfi
authors.forename: Gian Carlo
authors.initials: GC
authors.lastname: Gaboardi
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Tazzari
authors.forename: Andrea
authors.initials: A
authors.lastname: Pession
authors.forename: Kaoru
authors.initials: K
authors.lastname: Goto
authors.forename: Alberto M
authors.initials: AM
authors.lastname: Martelli
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002467:Cell Nucleus / Q000201:enzymology*; D019938:Cyclin D1 / Q000378:metabolism*; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D015536:Down-Regulation; D016193:G1 Phase; D016147:Genes, Tumor Suppressor; D017874:Immediate-Early Proteins / Q000378:metabolism*; D051379:Mice; D032446:Myoblasts / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D034741:RNA, Small Interfering / Q000378:metabolism; D025521:Tumor Suppressor Proteins
chemical_list: C489435:Btg2 protein, mouse; D017874:Immediate-Early Proteins; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D019852:Diacylglycerol Kinase; C512480:diacylglycerol kinase zeta, mouse