miRNA let-7 expression is regulated by glucose and TNF-α by a remote upstream promoter

miRNAs regulate protein abundance and control diverse aspects of cellular processes and biological functions in metabolic diseases, such as obesity and type 2 diabetes (T2D). Let (lethal)-7 miRNAs specifically targets genes associated with T2D and have been implicated in the regulation of peripheral glucose metabolism, yet the direct regulators of let-7 miRNA expression are unknown. In the present study, we report on a putative promoter region for the let-7a-1, let-7f-1 and let-7d gene cluster on chromosome 9 and characterize the promoter activity of this novel area. We show that promoter activity and let-7 miRNA expression is dynamically regulated in response to different factors including serum, glucose, tumour necrosis factor (TNF)-α and caffeine. These findings will contribute to understanding the interaction between precise promoter elements to control the transcription and translation of let-7 miRNA genes.