An auto-regulatory loop for EBV LMP2A involves activation of Notch

Area of Science:

• Virology
• Cell Biology
• Cancer Biology

Background:

• Latent membrane protein 2A (LMP2A) is found in Hodgkin's lymphoma, nasopharyngeal carcinoma, and Burkitt's lymphoma.
• LMP2A expression occurs independently of the transcriptional activator EBNA2, suggesting an alternative regulatory mechanism.
• The intracellular domain of Notch (Notch-IC) is a functional homolog of EBNA2, and microarray data suggest LMP2A may activate the Notch pathway.

Purpose of the Study:

• To investigate the hypothesis that LMP2A expression leads to constitutive Notch pathway activation, thereby auto-regulating its own promoter.
• To elucidate the mechanism behind EBNA2-independent LMP2A expression in Epstein-Barr virus (EBV)-associated malignancies.

Main Methods:

• Assessing Notch pathway activation by LMP2A in B cells and epithelial cells.
• Evaluating the role of LMP2A's amino-terminal signaling domain and specific tyrosine residues (31, 101, 112) in promoter activation.
• Analyzing the impact of deleting RBP-Jkappa consensus sequences on LMP2A promoter activity.

Main Results:

• LMP2A was found to constitutively activate the Notch pathway in both B cells and epithelial cells.
• Expression of LMP2A alone was sufficient to activate its own expression, requiring the amino-terminal signaling domain.
• Mutations in tyrosines 31, 101, and 112, and deletion of RBP-Jkappa sites significantly reduced LMP2A promoter activity.

Conclusions:

• LMP2A constitutively activates the Notch pathway to auto-regulate its promoter.
• LMP2A exploits the Notch pathway for self-regulation, potentially explaining its EBNA2-independent expression in EBV-associated cancers.