Requirement of CRTC1 coactivator for hepatitis B virus transcription

Tang, Hei-Man Vincent; Gao, Wei-Wei; Chan, Chi-Ping; Cheng, Yun; Chaudhary, Vidyanath; Deng, Jian-Jun; Yuen, Kit-San; Wong, Chun-Ming; Ng, Irene Oi-Lin; Kok, Kin-Hang; Zhou, Jie; Jin, Dong-Yan

Given that CRTC1 protein is abundant in HBV-infected cells, it will be of interest to assess the influence of CRTC coactivators on HBV transcription. CRTCs potentiate CREB-dependent transcription depending on the promoter context (32, 33) . Although CRE elements are found in preS2 and X promoters of HBV (10, 11) , it remains to be determined whether they are activated by CRTCs. With this in mind, we asked how CRTCs might affect transcriptional activity of these two promoters. All three CRTCs were expressed to comparable levels in HepG2 cells (Figure 2A ). Whereas all three CRTCs activated preS2 promoter significantly ( Figure 2B , groups 2-4 compared to 1), they had minimal or no influence on basal activity of X promoter in the same setting ( Figure 2C ). Hence, CRTCs are capable of activating HBV transcription from the preS2 promoter.