Phosphorylation of Serine 239 of Groucho/TLE1 by Protein Kinase CK2 Is Important for Inhibition of Neuronal Differentiation

Abstract

Transcriptional corepressors of the Groucho (Gro)/TLE family play important roles during a variety of developmental pathways, including neuronal differentiation. In particular, they act as negative regulators of neurogenesis, together with Hairy/Enhancer of split (Hes) DNA-binding proteins. The interaction with Hes1 leads to Gro/TLE hyperphosphorylation and increased transcription repression activity in mammalian cells, but the underlying molecular mechanisms are poorly characterized. We now show that Gro/TLE1 is phosphorylated in vivo by protein kinase CK2. This phosphorylation occurs at serine 239 within the conserved CcN domain present in all Gro/TLE family members. Mutation of serine 239 into alanine decreases Hes1-induced hyperphosphorylation of Gro/TLE1 and also reduces its nuclear association and transcription repression activity. We demonstrate further that Gro/TLE1 inhibits the transition of cortical neural progenitors into neurons and that its antineurogenic activity is inhibited by a serine-239-alanine mutation but not by a serine-239-glutamate mutation. These results suggest that CK2 phosphorylation of serine 239 of Gro/TLE1 is important for its function during neuronal differentiation.

Prolyl isomerase Pin1 and protein kinase HIPK2 cooperate to promote cortical neurogenesis by suppressing Groucho/TLE:Hes1-mediated inhibition of neuronal differentiation

“…[3][4][5] In both invertebrate and vertebrate species, Notch-induced Hes proteins, such as Hes1, repress transcription together with the general transcriptional corepressors of the Groucho/transducin-like Enhancer of split (Gro/TLE) family. [6][7][8] Gro/TLE1 is expressed in undifferentiated cortical neural progenitor cells in which Hes1 is also expressed [9][10][11] and inhibits cortical neuronal differentiation in vivo and in vitro. [10][11][12] Moreover, Hes1 and Gro/TLE1 physically interact, repress transcription together and localize to common promoter regions in vivo.…”

“…[6][7][8] Gro/TLE1 is expressed in undifferentiated cortical neural progenitor cells in which Hes1 is also expressed [9][10][11] and inhibits cortical neuronal differentiation in vivo and in vitro. [10][11][12] Moreover, Hes1 and Gro/TLE1 physically interact, repress transcription together and localize to common promoter regions in vivo. [13][14][15] Hes1 and Gro/TLE1 are expressed in neural progenitor cells during both the proliferative and differentiative phases of cortical neurogenesis, suggesting the existence of mechanisms that either promote or inhibit their anti-neurogenic function at different stages of cortical neuronal differentiation.…”

Characterization of Aes nuclear foci in colorectal cancer cells

“…These results may appear contradictory to the 'wine tannin hypothesis' if the soluble form of Aes-TLE1 complex is responsible for transcriptional inhibition. We speculate that being soluble is a necessary but not the sufficient feature for Aes-TLE1 to inhibit transcription, and that TLE1(S239A) is unable to interact with the Rbpj transcription factor complex as with other transcription factors (17,28).…”

“…3A left) (17,28). Therefore, we studied whether phosphorylation of TLE1(S239) was critical for the inhibition of Notch signalling-mediated transcription and/or focus formation with Aes.…”

“…cDNAs of Aes truncation mutants were constructed by PCR using wild-type Aes cDNA as a template, followed by sequencing. Expression construct for TLE1(S239A) was published previously (17).…”