A Role for Cell Cycle-regulated Phosphorylation in Groucho-mediated Transcriptional Repression

• Published in: The Journal of biological chemistry Vol. 277; no. 52; pp. 51049 - 51057
• Main Authors: Nuthall, Hugh N., Joachim, Kerline, Palaparti, Anuradha, Stifani, Stefano
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 27.12.2002; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Basic Helix-Loop-Helix Transcription Factors; CDC2 Protein Kinase - metabolism; Cell Cycle - drug effects; Cell Cycle - physiology; Cell Line; Cell Nucleus - physiology; DNA-Binding Proteins - metabolism; Drosophila; Enhancer Elements, Genetic; HeLa Cells; Humans; Jurkat Cells; Mitosis; Okadaic Acid - pharmacology; Phosphates - metabolism; Phosphorylation; Rats; Recombinant Proteins - metabolism; Repressor Proteins - metabolism; Rod Cell Outer Segment - physiology; Transcription, Genetic - drug effects; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111660200

Transcriptional corepressors of the Groucho/transducin-like Enhancer of split (Gro/TLE) family are involved in a variety of cell differentiation mechanisms in both invertebrates and vertebrates. They become recruited to specific promoter regions by forming complexes with a number of different DNA-binding proteins thereby contributing to the regulation of multiple genes. To understand how the functions of Gro/TLE proteins are regulated, it was asked whether their ability to mediate transcriptional repression might be controlled by cell cycle-dependent phosphorylation events. It is shown here that activation of p34cdc2 kinase (cdc2) with okadaic acid is correlated with hyperphosphorylation of Gro/TLEs. Moreover, pharmacological inhibition of cdc2 activity results in Gro/TLE dephosphorylation. In agreement with these findings, a purified cdc2-cyclin B complex can directly phosphorylate Gro/TLEsin vitro. Two separate Gro/TLE domains, the CcN and SP regions, contain sequences that are phosphorylated by cdc2. Deletion of these sequences is correlated with loss of Gro/TLE phosphorylation by cdc2 in vitro and okadaic acid-induced Gro/TLE hyperphosphorylation in vivo. In addition, Gro/TLEs are phosphorylated during the G2/M phase of the cell cycle, and this is correlated with a decreased nuclear interaction. Finally, the transcription repression ability of Gro/TLEs is enhanced by pharmacological inhibition of cdc2. Taken together, these results demonstrate that Gro/TLE proteins are phosphorylated as a function of the cell cycle and implicate phosphorylation events occurring during mitosis in the negative regulation of Gro/TLE activity.