CircPRKAA1 activates a Ku80/Ku70/SREBP1 axis driving de novo fatty acid synthesis in cancer cells

Many metabolism-related genes undergo alternative splicing to generate circular RNAs although their functions remain poorly understood. Here we report that circPRKAA1, a circRNA derived from the α1 subunit of AMPK, fulfils a fundamental role in maintaining lipid homeostasis. CircPRKAA1 expression facilitates fatty acid synthesis and promotes lipid storage through two coordinated functions. First, circPRKAA1 promotes a tetrameric complex between the Ku80/Ku70 heterodimer and the mature form of sterol regulatory element-binding protein-1 (mSREBP1) to enhance the stability of mSREBP1. Secondly, circPRKAA1 selectively binds to the promoters of the ACC1, ACLY, SCD1 and FASN genes to recruit mSREBP1, upregulating their transcription and increasing fatty acid synthesis to promote cancer growth. Moreover, circPRKAA1 biogenesis is negatively regulated by AMPK activity with lower AMPK activation in hepatocellular carcinoma tissues frequently associated with elevated circPRKAA1 expression. Together, this work identifies circPRKAA1 as an integral element of AMPK-regulated reprogramming of lipid metabolism in cancer cells. Comparative gene expression profiling analysis of RNA-seq data for HepG2 cells with circPRKAA1 Knockdown