SIRT1 regulates Tat-induced HIV-1 transactivation through activating AMP-activated protein kinase

Transcription of human immunodeficiency virus (HIV-1) is activated by viral Tat protein which regulates HIV-long terminal repeat (LTR) transcription and elongation. HIV-1 Tat protein is a substrate for the deacetylase activity of sirtuin 1 (SIRT1). Here we investigate the signaling pathway involved in Tat-induced HIV-1 transactivation through SIRT1. Western blot analysis showed a significant reduction in AMPK activation and downstream acetyl-CoA carboxylase (ACC) activation in response to Tat treatment. NAD(+) levels and SIRT1 activity were also decreased with Tat treatment. SIRT1 activator resveratrol reversed Tat-mediated reduction in AMPK activation and downstream ACC activation; while SIRT1 inhibitor nicotinamide or knockdown of SIRT1 by siRNA potentiated Tat-mediated reduction in AMPK activation and downstream ACC activation. Consistent with this association, AMPK activator AICAR as well as resveratrol inhibited Tat-induced HIV-1 transactivation. On the contrary, AMPK inhibitor compound C, knockdown of AMPK by siRNA as well as nicotinamide or knockdown of SIRT1 by siRNA potentiated Tat-induced HIV-1 transactivation. Collectively, our data provide new insights into understanding of the molecular mechanisms of Tat-regulated transcription, suggesting that targeting SIRT1-AMPK pathway could serve as a new target for the development of new anti HIV-1 agents. (C) 2009 Elsevier B.V. All rights reserved.