TRF2 Inhibition-Mediated Degradation Derepresses the Neuronal Differentiation Program

Telomere binding factor 2 (TRF2), is a protein that plays a major role in the maintenance of telomere integrity. In mitotic normal and transformed cells, TRF2 inhibition triggers a rapid telomere DNA damage response that results in cell senescence or apoptosis. Here we provide evidence that TRF2 plays a role suppressing neuronal differentiation. TRF2 interacts with the RE1-silencing transcription factor (REST) in nuclear PML protein-containing compartments of neuronal cells in vivo. Inhibition of TRF2 function with a dominant-negative form of TRF2 elicits a telomeric DNA damage response, and disrupts the TRF2-REST complex resulting in proteasomal degradation of REST. Overexpression of REST impairs the ability of DN-TRF2 to induce neuronal differentiation, indicating that enhanced degradation of REST is sufficient to account for the differentiation-inducing effect of DN-TRF2. REST degradation derepresses RE1-regulated genes (L1CAM, BDNF, b3-tubulin, syntaxin and others) resulting in morphological and functional differentiation of neurons. Our findings identify a novel interaction between the telomeric protein TRF2 and REST which regulates the molecular differentiation program of neurons. Keywords: transfection and molecular inhibition Cells were transfected with GFP vector, WT-TRF2 or DN-TRF2, and were maintained under G418 selection for 7 days. To confirm an inhibitory effect of DN-TRF2 on cell proliferation cells were counted daily during a 4 day post-transfection period. Gene array analysis was performed using NIA MGC1 9600 human gene cDNA microarray on 6 samples; 3 controls and 3 DN-TRF2 positive.