Long-Range Regulatory Synergy Is Required to Allow Control of the TAC1 Locus by MEK/ERK Signalling in Sensory Neurones

Abstract

Changes in the expression of the neuropeptide substance P (SP) in different populations of sensory neurones are associated with the progression of chronic inflammatory disease. Thus, understanding the genomic and cellular mechanisms driving the expression of the TAC1 gene, which encodes SP, in sensory neurones is essential to understanding its role in inflammatory disease. We used a novel combination of computational genomics, primary-cell culture and mouse transgenics to determine the genomic and cellular mechanisms that control the expression of TAC1 in sensory neurones. Intriguingly, we demonstrated that the promoter of the TAC1 gene must act in synergy with a remote enhancer, identified using comparative genomics, to respond to MAPK signalling that modulates the expression of TAC1 in sensory neurones. We also reveal that noxious stimulation of sensory neurones triggers this synergy in larger diameter sensory neurones – an expression of SP associated with hyperalgesia. This noxious stimulation of TAC1 enhancer-promotor synergy could be strongly blocked by antagonism of the MEK pathway. This study provides a unique insight into the role of long-range enhancer-promoter synergy and selectivity in the tissue-specific response of promoters to specific signal transduction pathways and suggests a possible new avenue for the development of novel anti-inflammatory therapies.

Differential Activity by Polymorphic Variants of a Remote Enhancer that Supports Galanin Expression in the Hypothalamus and Amygdala: Implications for Obesity, Depression and Alcoholism

“…Using these cells, we were unable to show that GAL5.1 could act as an enhancer of promoter activity. However, we have previously shown that many regulatory sequences are only able to act as enhancers in response to activation of an appropriate signal transduction cascade (Shanley et al, 2010(Shanley et al, , 2011. Thus, we were able to show that GAL5.1 acted as an enhancer of promoter activity following activation of the PKC pathway, which is known to modulate gene expression in the hypothalamus and amygdala, but not PKA or MAPkinase pathways.…”

“…ECR2 could only drive tissue-specific expression in the presence of the endogenous TAC1 promoter whereas GAL5.1 can support expression in the presence of an exogenous weak promoter such as the human b-globin promoter or HSV-TK promoter. These observations suggest that different enhancers possess varying levels of autonomy or interdependence and that the GAL5.1 is functionally self-contained relative to some other previously characterized enhancers (Shanley et al, 2010(Shanley et al, , 2011.…”

“…We have previously shown that comparative genomic analysis is an effective method of detecting functional gene regulatory regions (Davidson et al, 2006a, b;Mackenzie et al, 1997Mackenzie et al, , 2004aMacKenzie and Quinn, 2004b;Miller et al, 2007Miller et al, , 2008Shanley et al, 2010). We carried out comparative analysis of 100 kb of the genome surrounding the human GAL locus (Figures 1a and b) using the monkey, dog, mouse, rat, opossum, and chicken genomes and succeeded in identifying an area of homology that was located 42 kb 5 0 of the GAL transcriptional start site that we called GAL5.1.…”

“…Thus, it would be interesting to see how GAL5.1 interacted with the GAL promoter regions previously identified (Bacon et al, 2007). Moreover, an interesting contrast can be drawn between GAL5.1 and the ECR2 enhancer shown to control the expression of the TAC1 gene in sensory neurones (Shanley et al, 2010(Shanley et al, , 2011. ECR2 could only drive tissue-specific expression in the presence of the endogenous TAC1 promoter whereas GAL5.1 can support expression in the presence of an exogenous weak promoter such as the human b-globin promoter or HSV-TK promoter.…”

SVA retrotransposons as modulators of gene expression

“…Our own studies on the endogenous expression of the neuropeptide, substance P encoded by the TAC1 gene demonstrated that although the gene itself from 5′ to 3′ UTR was 8kb, we required a DNA fragment of 350kb to reproduce the appropriate expression patterns 30 , 31 . Subsequently our collaborators demonstrated key regulatory domains were as far as 250 kb and 100 kb 5′of the TAC1 gene 32 . The 350kb TAC1 fragment as a transgenic insertion demonstrated not only the well characterized rodent expression of TAC1, but as was the case with the SLC6A4 VNTR, it also demonstrated human specific TAC1 expression patterns and we again argued that the DNA was taking advantage of the complement of transcription factor that was present in the cells when the DNA in the regulatory regions evolved to support distinct transcription profiles for this gene.…”