Lamin A/C promotes HBV transcription by modulating histone modification associated with cccDNA minichromosome in an HBx-dependent manner.

Background: Chronic hepatitis B virus (HBV) infection remains a serious public health challenge, and primary treatment strategies are unable to cure HBV infection due to the persistence of HBV covalently closed circular DNA (cccDNA) in the nuclei of cells. The HBV X protein (HBx) plays a crucial role in regulating cccDNA transcription. Therefore, targeting HBx to identify host proteins that regulate cccDNA transcription could represent a curative approach.

Methods: Here, we used co-immunoprecipitation (co-IP) and mass spectrometry (MS) to identify proteins that interact with HBx. The candidate proteins Lamin A and C (Lamin A/C) were knocked down by RNA interference, and Lamin A/C was overexpressed via lentiviral vectors in HBV-infected cell cultures. Chromatin immunoprecipitation (ChIP) followed by quantitative PCR (ChIP-qPCR) was used to investigate protein-DNA interactions.

Results: A mechanistic study revealed that Lamin A/C bound to HBx, resulting in reduced degradation of HBx by the 26S proteasome. Moreover, Lamin A/C regulated HBV cccDNA transcription in vitro, which was associated with HBx. In addition, Lamin A/C knockdown resulted in transcriptional silencing of the HBV cccDNA but not in HBV-HBx-deficient (∆HBx)-infected cells. Importantly, experimental knockdown of Lamin A/C reduced the level of active histone modifications (H3K4me3 and H3k27Ac) bound to cccDNA and increased the level of inhibited histone modifications (H3K9me3 and H3K27me3) bound to cccDNA, which was suppressed in the HBV-∆HBx system.

Conclusion: Our findings reveal that Lamin A/C acts as a new host factor for HBV cccDNA through an epigenetic regulatory mechanism that can interact with HBx and prevent its degradation.