Coordinated regulation of IFITM1, 2 and 3 genes by an IFN-responsive enhancer through long-range chromatin interactions

Publication date: Available online 13 May 2017
Source:Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms
Author(s): Ping Li, Ming-Lei Shi, Wen-Long Shen, Zhang Zhang, De-Jian Xie, Xiang-Yuan Zhang, Chao He, Yan Zhang, Zhi-Hu Zhao
Interferon-induced transmembrane protein (IFITM) 1, 2 and 3 are a family of interferon (IFN)-induced transmembrane proteins that block entry of a broad spectrum of pathogens. However, the transcriptional regulation of these genes, especially whether there exists any enhancers and their roles during the IFN induction process remain elusive. Here, combining episomal luciferase reporter assay and in vivo genome editing, we identified an IFNβ-responsive enhancer located 35kb upstream of IFITM3 gene promoter upregulating the IFNβ-induced expression of IFITM1, 2 and 3 genes, thus contributing to IFNβ-mediated resistance to influenza A virus (IAV) infection. The enhancer was first identified and verified by data mining and luciferase reporter assay. Then we showed that signal transducers and activators of transcription (STAT) 1 bound to the enhancer after the treatment of IFNβ and was indispensable for the enhancer activity. Next, CRISPR-Cas9 mediated in vivo truncation of the enhancer considerably decreased both IFNβ and IAV-induced expression of IFTIM1, 2 and 3 in HEK293 cells. Furthermore, chromosome conformation capture revealed that the IFITM1, 2 and 3 genes physically clustered together and constitutively looped to the distal enhancer through long-range interactions in both HEK293 and A549 cells, providing structural basis for coordinated regulation of IFITM1, 2 and 3 by IFNβ. Finally, we showed that in vivo truncation of the enhancer impaired IFNβ-induced resistance to IAV infection. These findings expand our understanding of the mechanisms underlying the transcriptional regulation of IFITM1, 2 and 3 expression and its ability to mediate IFN-β signaling.



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