DHX15 inhibits mouse APOBEC3 deamination.

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.