A Novel cccDNA-Binding Protein HSPA1B Promotes HBV Transcription and HBx-Mediated HCC Metastasis via Downregulating SOX4.

Hepatocellular carcinoma (HCC) occurrence and progression are closely associated with hepatitis B virus (HBV) infection. Heat shock protein family A member 1B (HSPA1B), a key member of the heat shock protein 70 family, has attracted extensive attention in viral infection research, yet its specific function in HBV-related HCC pathogenesis remains largely unknown. HSPA1B was identified as a cccDNA-binding protein using the biotin-avidin system, and its role in HBV infection and HCC progression was systematically investigated. In vivo experiments were performed using a mouse model established by tail vein injection of prcccDNA and pCMV-KRAB-Cre to evaluate the impact of HSPA1B on HBV transcription and replication. RNA sequencing was applied to HBV-infected HepG2-NTCP cells to analyze the differentially expressed genes regulated by HSPA1B, aiming to clarify the molecular mechanism underlying HSPA1B-mediated promotion of HBV transcription and replication. Meanwhile, Western blot, RT-qPCR, co-immunoprecipitation and Transwell assays were used to explore the relationship between HSPA1B and HBV-related HCC. We found that HSPA1B promoted HBV transcription and replication. Mechanistically, the increased expression of HSPA1B promoted HBV transcription and replication by downregulating SOX4 and enhancing the stability of the HBx protein. Further research indicated that HSPA1B can enhance the metastasis and invasion of HBx-mediated HCC. Collectively, these results demonstrate a novel function of HSPA1B in regulating HBV transcription and HBV-related HCC metastasis, indicating that HSPA1B may serve as a promising therapeutic target for HBV-associated HCC.