Sequential backbone chemical shift assignments of a cancer-associated isoform of the HBx protein from human hepatitis B virus.

Chronic infections with hepatitis B virus (HBV) are a leading cause of liver cirrhosis and hepatocellular carcinoma worldwide. Among the four viral proteins encoded by HBV, the X protein (HBx) has remained resistant to atomic-level characterization. HBx is a small, non-structural protein that interacts with various human host proteins. It is essential for HBV replication and implicated in HBV-induced carcinogenesis. Here, we present the sequential backbone resonance assignments of a C-terminally truncated HBx isoform (residues 1–120), which is frequently found in chronically infected patients. Three-dimensional NMR experiments were recorded in the presence of residual urea (1 M), and the assignments of amide moieties were subsequently transferred to a low-urea condition (< 0.2 M) compatible with HBx interaction studies. We compare manual assignments with automated predictions using the ARTINA software. These results reveal secondary structure propensities in the truncated HBx isoform and lay the groundwork for future NMR-based studies of HBx interactions in solution.