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Nuclear translocation of aflatoxin B1 - protein complex
J J Ch'ih1, J I Ewaskiewicz, P Taggart
1Department of Biological Chemistry, Hahnemann University, School of Medicine, Philadelphia, PA 19102-1192.
Biochemical and Biophysical Research Communications
|January 15, 1993
Summary
Aflatoxin B1 (AFB1) binds to proteins, with pyruvate kinase showing the highest affinity. Nuclear translocation and activation of AFB1-protein complexes are facilitated by proteins with nuclear localization signals (NLS).
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Aflatoxin B1 (AFB1) is a mycotoxin with significant toxicological implications.
- Understanding AFB1-protein interactions is crucial for elucidating its cellular mechanisms of action.
- Nuclear translocation is a key step in the activation and subsequent genotoxicity of AFB1.
Purpose of the Study:
- To investigate the in vitro binding affinity of [3H]-AFB1 to various proteins.
- To examine the role of proteins, particularly those with nuclear localization signals (NLS), in AFB1 nuclear translocation and activation.
- To determine the impact of AFB1-protein complex formation on its activation and adduct formation within isolated rat liver nuclei.
Main Methods:
- Equilibrium dialysis was employed to quantify the in vitro binding of [3H]-AFB1 to proteins.
- Isolated rat liver nuclei were used to study nuclear translocation and activation of AFB1-protein complexes.
- An ATP and NADPH regenerating system was utilized to mimic cellular conditions for activation studies.
Main Results:
- A distinct hierarchy of [3H]-AFB1 binding activity was observed, with pyruvate kinase exhibiting the highest affinity, followed by albumin-NLS, albumin, carbonic anhydrase, RNase, and histones.
- Proteins containing nuclear localization signals (NLS), such as histones and albumin-NLS, significantly facilitated the translocation of AFB1 into the nucleus.
- Within the nucleus, AFB1 underwent activation and subsequent adduct formation, indicating that nuclear entry is a prerequisite for these processes.
Conclusions:
- Protein binding influences AFB1's interaction with cellular components, with specific proteins enhancing its nuclear uptake.
- Nuclear localization signals play a critical role in mediating AFB1's entry into the nucleus, a key step for its activation.
- The findings highlight the importance of protein-AFB1 complex formation in the toxicological pathway of AFB1, particularly concerning nuclear events.