# How does a metallocofactor in the Hepatitis B viral protein X orchestrate pathogenesis and liver cancer?

> **NIH NIH R01** · BRANDEIS UNIVERSITY · 2022 · $338,054

## Abstract

Project Summary
 Chronic infection by the Hepatitis B virus (HBV) is a leading cause of human cancer worldwide, and is
strongly associated with development of cirrhosis and hepatocellular carcinoma (HCC). The 17-kDa HBx protein
of HBV is a causative tumorigenic agent and affects multiple cellular processes, either on its own or together
with the proteins it targets. Though the oncogenic potential of HBx has been demonstrated, neither its structure
nor the molecular mechanisms by which it mediates liver-associated diseases are known. The major obstacles
have been the sparing solubility, lack of significant homology to characterized proteins and intrinsic disorder. Our
studies have succeeded in obtaining HBx in highly soluble forms and for the first time shown that HBx is an [Fe-
S]-binding protein. Our long-term goal is to establish the chemical nature of the cofactor and its involvement in
driving protein conformation and reactivities, ultimately translating this molecular and structural knowledge to
HBxs’ extended functional repertoire. Our central hypothesis is that the [Fe-S] cluster is a common feature of
HBxs across all genotypes. We propose that the [Fe-S] cofactor confers structure in an otherwise disordered
protein and modulates protein reactivity and interactions by (at least) three distinct pathways: a) protein-protein
interactions, by changing the oligomeric or conformational status of HBx, b) redox mechanisms involving either
i) electron transfer processes to cofactors of target proteins or ii) regulatory processes as a response to cellular
redox status and generation of ROS, c) Fe- or [Fe-S]- transfer mechanisms, by which HBx can act as a scaffold
for iron-trafficking to regulate iron homeostasis and downstream molecular pathways. Our specific aims will test
these hypotheses by: (Aim 1) establishing the biologically relevant form of the cofactor, and if both observed
[4Fe] (stable) and [2Fe] (transient) forms are physiologically relevant. We will identify the cluster ligands, cysteine
residues likely involved in disulfides and examine how clinical mutations and large sequence deletions may affect
the cofactor and thus HBx function. (Aim 2) Establish the type, location and effects of the [Fe-S] cluster on the
protein structure (disorder-to-order transition) and whether cluster incorporation drives protein folding. If
successful, this step will set the stage for solving by solution NMR methods the highly sought structure of HBx,
either on its own or together with cellular binding partners. (Aim 3) Establish a link between the type and redox
form of the [Fe-S] cofactor and HBx biological activity. The expected overall impact of this innovative proposal
is that it will fundamentally advance our understanding of HBx on the molecular and structural level, which is
currently missing. Because HBx is a potential target for the development of anti-cancer drugs, determining the
role(s) of the [Fe-S] cofactor and the linked structure/function re...

## Key facts

- **NIH application ID:** 10428574
- **Project number:** 5R01GM126303-04
- **Recipient organization:** BRANDEIS UNIVERSITY
- **Principal Investigator:** Maria-Eirini Pandelia
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $338,054
- **Award type:** 5
- **Project period:** 2019-07-05 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10428574

## Citation

> US National Institutes of Health, RePORTER application 10428574, How does a metallocofactor in the Hepatitis B viral protein X orchestrate pathogenesis and liver cancer? (5R01GM126303-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10428574. Licensed CC0.

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