Functional interactions between herpesvirus oncoprotein MEQ and cell cycle regulator CDK2

Area of Science:

• Oncogenesis
• Molecular Virology
• Cell Cycle Regulation

Background:

• Marek's disease virus (MDV) is an avian alphaherpesvirus utilized as a model for herpesvirus oncogenesis.
• The MEQ protein of MDV is a potential oncogene capable of transforming rodent fibroblasts.
• MEQ induces morphological transformation, anchorage- and serum-independent growth, and protects cells from apoptosis.

Purpose of the Study:

• To investigate the interaction between the MEQ oncoprotein and cell cycle regulators.
• To determine the subcellular localization and functional consequences of MEQ and CDK2 association.
• To elucidate the role of MEQ phosphorylation in its subcellular localization and DNA binding activity.

Main Methods:

• Immunofluorescence microscopy to observe protein colocalization.
• In vitro kinase assays to assess MEQ phosphorylation by CDKs.
• Site-directed mutagenesis to create MEQ phosphorylation site mutants.
• Indirect immunofluorescence to study mutant protein localization.

Main Results:

• MEQ protein colocalizes with cyclin-dependent kinase 2 (CDK2) in coiled bodies and nucleolar periphery during G1/S phase.
• CDK2 localization to coiled bodies is specific to MEQ-transformed cells, indicating MEQ influences CDK2 localization.
• Phosphorylation of MEQ by CDKs, particularly at serine 42, promotes cytoplasmic translocation and reduces DNA binding activity.

Conclusions:

• MEQ oncoprotein interacts with CDK2 in a cell cycle-dependent manner.
• Phosphorylation of MEQ by CDK2 regulates its subcellular localization and DNA binding.
• A novel reciprocal modulation exists between the herpesvirus oncoprotein MEQ and CDK2.