Transcriptional Activation of REST by Sp1 in Huntington's Disease Models

Abstract

In Huntington's disease (HD), mutant huntingtin (mHtt) disrupts the normal transcriptional program of disease neurons by altering the function of several gene expression regulators such as Sp1. REST (Repressor Element-1 Silencing Transcription Factor), a key regulator of neuronal differentiation, is also aberrantly activated in HD by a mechanism that remains unclear. Here, we show that the level of REST mRNA is increased in HD mice and in NG108 cells differentiated into neuronal-like cells and expressing a toxic mHtt fragment. Using luciferase reporter gene assay, we delimited the REST promoter regions essential for mHtt-mediated REST upregulation and found that they contain Sp factor binding sites. We provide evidence that Sp1 and Sp3 bind REST promoter and interplay to fine-tune REST transcription. In undifferentiated NG108 cells, Sp1 and Sp3 have antagonistic effect, Sp1 acting as an activator and Sp3 as a repressor. Upon neuronal differentiation, we show that the amount and ratio of Sp1/Sp3 proteins decline, as does REST expression, and that the transcriptional role of Sp3 shifts toward a weak activator. Therefore, our results provide new molecular information to the transcriptional regulation of REST during neuronal differentiation. Importantly, specific knockdown of Sp1 abolishes REST upregulation in NG108 neuronal-like cells expressing mHtt. Our data together with earlier reports suggest that mHtt triggers a pathogenic cascade involving Sp1 activation, which leads to REST upregulation and repression of neuronal genes.

Perturbations of Neuron-Restrictive Silencing Factor Modulate Corticotropin-Releasing Hormone Gene Expression in the Human Cell Line BeWo

“…We also show that NRSF-mediated modulation of CRH is coupled with activation of signaling pathways mediated by cAMP. We observed a novel relationship indicating that cAMP pathway activation can lead to downregulation of the NRSF splice variant driven by promoter c. It has been previously shown in non-human primates and rodents that the transcription factor SP1 has binding sites across the NRSF promoter, although the region of NRSFc is solely regulated by SP1 and has the highest binding sites per promoter [34]. Through sequence investigation of the promoters we observed a similar but less extensive pattern of SP1 regulation in the human NRSF.…”

Restricted Transgene Expression in the Brain with Cell-Type Specific Neuronal Promoters

“…Scale bar = 20 lm. Chiang et al, 2007;Ravache et al, 2010), Dlx5/6 transcriptional activity was lower than in animals expressing a wildtype Htt fragment. In contrast, the Tac1 promoter was unaffected by the expression of mutant Htt.…”

Regulation of RE1 Protein Silencing Transcription Factor (REST) Expression by HIP1 Protein Interactor (HIPPI)

“…In neuronal cells, REST expression is activated by YY1, DYRK1A, and Wnt/TCF signaling (33)(34)(35). Recently, transcription factor Sp1 has been shown to regulate REST expression in undifferentiated NG108 cells as well as in a mouse model of HD (36). Additionally, a double negative feedback loop involving REST-dependent expression of microRNA 9 and 9* controls REST expression in HD (37).…”

“…Many of the REST target genes have been shown to be down-regulated in HD (15). Moreover, there are reports indicating an overall increase in REST expression in various models of HD (25,36,39). The importance of REST in regulating HD pathogenesis inspired us to investigate whether HIPPI-mediated up-regulation of REST plays any role in HD.…”