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HIV-1 Rev transactivator: a beta-subunit directed substrate and effector of protein kinase CK2
F Meggio1, O Marin, M Boschetti
1Dipartimento di Chimica Biologica, Centro di Studio delle Biomembrane del CNR, Padova, Italy. meggio@civ.bio.unipd.it
Abstract:
The phosphorylation of HIV-1 Rev by protein kinase CK2 is strictly dependent on the regulatory beta subunit of the kinase and is deeply affected by conformational changes of the substrate outside the phosphorylation site. Here we show that Rev modulates a variety of CK2 properties, including autophosphorylation, catalytic activity toward calmodulin, and susceptibility to polycationic effectors, whose common denominator is the involvement of the beta subunit. Rev's two major CK2 sites are located at its N-terminus, immediately adjacent to a helix-loop-helix motif. By comparing the behaviour of full-size Rev with that of synthetic peptides reproducing, with suitable modifications, its N-terminal 26 amino acids including the phosphoacceptor site (Ser 5, Ser 8) and amphipathic helix-1, it appears that the functional interaction of the N-terminal portion of Rev with the N-terminal domain of the beta subunit must rely on both electrostatic and hydrophobic interactions. The former mainly involve Rev's arginine-rich domain (residues 35-50) in helix-2, while the latter are mostly mediated by residues 12-24 of helix-1. These data disclose the possibility that, besides displaying protective, regulatory and targeting properties with respect to the catalytic subunit, the CK2 beta subunit also plays a role as a docking site for a subset of CK2 substrates.
Insights
HIV-1 Rev phosphorylation by protein kinase CK2 requires its beta subunit. Rev influences CK2 activity and interacts with the beta subunit via electrostatic and hydrophobic forces, suggesting the beta subunit acts as a substrate docking site.
Area of Science:
- Molecular Biology
- Virology
- Biochemistry
Background:
- Protein kinase CK2 (casein kinase 2) plays a crucial role in various cellular processes.
- The human immunodeficiency virus type 1 (HIV-1) Rev protein regulates viral gene expression.
- CK2-mediated phosphorylation of HIV-1 Rev is essential for its function and is known to be regulated by the CK2 beta subunit.
Purpose of the Study:
- To investigate how HIV-1 Rev modulates protein kinase CK2 properties.
- To elucidate the interaction mechanism between HIV-1 Rev and the CK2 beta subunit.
- To determine the role of the CK2 beta subunit in substrate recognition and regulation.
Main Methods:
- Comparative analysis of full-size Rev and synthetic peptides.
- Investigation of CK2 autophosphorylation and catalytic activity.
- Assessment of Rev's influence on CK2 susceptibility to polycationic effectors.
Main Results:
- HIV-1 Rev modulates CK2 autophosphorylation, catalytic activity, and effector susceptibility, with the beta subunit being central to these effects.
- The N-terminal region of Rev, including phosphorylation sites (Ser 5, Ser 8), interacts with the CK2 beta subunit's N-terminal domain.
- Both electrostatic interactions (involving Rev's arginine-rich domain) and hydrophobic interactions (involving helix-1 residues) mediate the Rev-beta subunit functional interaction.
Conclusions:
- The CK2 beta subunit is not only a regulatory component but also acts as a docking site for specific CK2 substrates like HIV-1 Rev.
- Understanding these interactions provides insights into the regulation of viral protein phosphorylation and CK2 substrate specificity.
- The findings highlight a dual role for the CK2 beta subunit in kinase regulation and substrate targeting.