SIRT1 enhances hepatitis virus B transcription independent of hepatic autophagy.

Autophagy is an intracellular process that can lead to the degradation of malfunctioned proteins and damaged organelles to maintain homeostasis during cellular stress. Here, we evaluated the change in hepatitis B virus (HBV) production by regulating hepatic autophagy in HBV-producing cells. We examined focusing on a relation with a positive autophagy regulator, sirtuin1 (SIRT1). Starvation and rapamycin treatment induced autophagy with increasing SIRT1 protein, HBc protein and pregenomic RNA (pgRNA) levels in HBV- producing cells. Knockdown of Atg7 or Atg13 suppressed hepatic autophagy, and it did not change SIRT1 protein, HBc protein or pgRNA levels in HBV- producing cells. Resveratrol, which increases SIRT1 expression and activity, promoted autophagy and increased HBc protein and pgRNA levels. siRNA-mediated knockdown of SIRT1 inhibited autophagy and decreased HBc protein and pgRNA levels. In SIRT1-knockdown cells, starvation promoted autophagy but did not increase HBc protein and pgRNA levels. In conclusion, HBc protein and pgRNA levels are upregulated not by the autophagic process itself but by the SIRT1 expression level.