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HIV-1 reverse transcriptase is phosphorylated in vitro and in a cellular system.
1Sealy Center for Molecular Science, The University of Texas Medical Branch Galveston, TX 77555-0851, USA. hi@st-and.ac.uk
The International Journal of Biochemistry & Cell Biology
|January 21, 2000
Summary
Phosphorylation can modify HIV-1 reverse transcriptase (RT) activity. While HIV-1 RT is phosphorylated by kinases in vitro and in insect cells, it shows little phosphorylation in infected human cells.
Area of Science:
- Biochemistry
- Virology
- Molecular Biology
Background:
- Phosphorylation is a key post-translational modification regulating protein function, particularly for nucleic acid-binding proteins.
- Human Immunodeficiency Virus type 1 (HIV-1) reverse transcriptase (RT) is crucial for viral replication.
- Potential phosphorylation sites on HIV-1 RT suggest a regulatory role for this modification.
Purpose of the Study:
- To investigate the phosphorylation of HIV-1 RT.
- To determine if phosphorylation regulates HIV-1 RT metabolism.
- To examine HIV-1 RT phosphorylation in vitro and in vivo.
Main Methods:
- Recombinant unphosphorylated HIV-1 RT heterodimer was expressed in bacteria.
- In vitro phosphorylation assays were performed using purified mammalian protein kinases.
- In vivo phosphorylation was assessed using an insect baculovirus expression system and HIV-1 infected H9-lymphoma cells.
Main Results:
- Five out of seven tested mammalian protein kinases phosphorylated HIV-1 RT in vitro.
- HIV-1 RT was phosphorylated in vivo when expressed in insect cells via a baculovirus system.
- HIV-1 RT immunoprecipitated from HIV-1 infected H9-lymphoma cells exhibited negligible phosphorylation.
Conclusions:
- Purified HIV-1 RT is a substrate for multiple mammalian protein kinases.
- HIV-1 RT can undergo phosphorylation during expression in insect cells.
- Phosphorylation of HIV-1 RT in human cells during active HIV-1 infection appears minimal, suggesting limited regulatory roles in vivo.