Combined C-terminal truncation and point mutations in HBx in genotype D1 HBV-associated hepatocellular carcinoma

<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Hepatitis B virus (HBV) infection remains a major global cause of hepatocellular carcinoma (HCC), with the X protein (HBx) playing a central role in viral replication and host-virus interactions. Genetic variability within HBx, particularly in genotype D1, may influence disease progression through structural and functional alterations.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>In this study, the HBx region from an HBV-infected patient with HCC was analyzed using high-resolution melting (HRM) and direct sequencing. The obtained sequence was compared with a genotype D1 reference, followed by in silico structural interpretation.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Sequence analysis revealed a distinct mutational profile characterized by multiple amino acid substitutions within the transactivation domain, including H94R, S101S (synonymous), L116S, and V131T, along with a C-terminal truncation spanning amino acids 142–154 (C-terminal deletion/truncation). These alterations were located within or adjacent to functionally important regions, including domains implicated in transcriptional regulation, mitochondrial signaling, and protein-protein interactions. HRM analysis demonstrated a shift in melting temperature consistent with altered nucleotide composition. Structural interpretation suggested that the combined presence of point mutations and C-terminal truncation may contribute to localized conformational changes and altered interaction potential, although no definitive functional conclusions can be drawn.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>The identified HBx variant represents a complex mutational pattern involving both non-synonymous substitutions and a C-terminal truncation, which may reflect a multi-step process of structural and functional perturbations. This observation expands the current understanding of HBx variability in genotype D1 HBV and highlights the potential relevance of combined mutational profiles in the context of HBV-associated hepatocarcinogenesis. Further studies are required to clarify the biological significance of these findings.</jats:p> </jats:sec>