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DHX15 inhibits mouse APOBEC3 deamination
Wenming Zhao1, Ayan Modak1, Susan R Ross1
1Department of Microbiology and Immunology, University of Illinois Chicago College of Medicine, Chicago, Illinois, United States of America.
Abstract:
APOBEC3 family proteins are critical host factors that counteract and prevent the replication of retroviruses and other viruses through cytidine deamination. Human APOBEC3 proteins inactivate HIV-1 through the introduction of lethal mutations to viral genomes. In contrast, mouse APOBEC3 does not induce DNA hypermutation of murine retroviruses, although it retains functional cytidine deaminase activity. Why mouse APOBEC3 does not effectively deaminate murine retroviruses is still unknown. In this study, we found that the dead box helicase DHX15 interacts with mouse APOBEC3 and inhibits its deamination activity. DHX15 was packaged into murine leukemia virus (MLV) virions independent of its binding with APOBEC3. Moreover, DHX15 knockdown inhibited MLV replication and resulted in more G-to-A mutations in proviral DNA. Finally, DHX15 knockdown induced DNA damage in murine cells, suggesting that it plays a role in preserving genome integrity in cells expressing mouse APOBEC3 protein.
Insights
Mouse APOBEC3 (A3) protein
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- APOBEC3 proteins are crucial for innate immunity against viral infections.
- Human APOBEC3 inactivates HIV-1 via cytidine deamination, but mouse APOBEC3 (mA3) does not effectively target murine retroviruses.
- The mechanism behind mA3's limited antiviral activity remains unclear.
Purpose of the Study:
- To investigate the interaction partners of mA3.
- To elucidate the mechanism by which mA3's antiviral activity is regulated.
- To understand the role of mA3 in host defense against murine retroviruses.
Main Methods:
- Co-immunoprecipitation assays to identify mA3 interacting proteins.
- In vitro cytidine deaminase activity assays.
- Murine leukemia virus (MLV) replication assays.
- Western blotting and quantitative PCR for gene knockdown analysis.
- Analysis of proviral DNA mutations and cellular DNA damage.
Main Results:
- The dead box helicase DHX15 was identified as an interactor of mA3, inhibiting its deamination activity.
- DHX15 is incorporated into MLV virions independently of mA3.
- Knockdown of DHX15 enhanced MLV replication and increased G-to-A mutations in proviral DNA.
- DHX15 knockdown led to DNA damage in murine cells.
Conclusions:
- DHX15 negatively regulates mA3's antiviral cytidine deaminase activity.
- DHX15 plays a role in MLV replication and potentially in maintaining genome integrity in cells expressing mA3.
- Understanding the DHX15-mA3 interaction provides insights into host-pathogen interactions and retroviral restriction mechanisms.
