Immediate-early protein 2 (IE2)

Immediate-early protein 2 (IE2) is a critical regulatory protein of Human Cytomegalovirus (HCMV) encoded by the UL122 gene [7, 9]. It is one of the first proteins expressed during the lytic cycle and is essential for the initiation of viral replication [10, 12]. IE2 functions as a potent transcriptional transactivator that triggers the expression of viral early and late genes required for DNA synthesis and virion assembly [7, 12]. Additionally, it exhibits negative autoregulatory activity by binding to the major immediate-early promoter (MIEP) to control its own expression levels [12, 18]. The protein also interacts with numerous host cellular factors to subvert the cell cycle and antagonize the innate immune response, facilitating viral persistence [10, 15]. Because of its indispensable role in the HCMV life cycle, IE2 was the target of fomivirsen, the first antisense oligonucleotide therapy approved by the FDA [1, 3]. Fomivirsen works by binding to IE2 mRNA, thereby preventing the translation of the protein and blocking viral replication [2, 5]. Although fomivirsen was later withdrawn from the market due to the declining incidence of CMV retinitis in the era of highly active antiretroviral therapy (HAART), IE2 remains a significant focus for developing novel antiviral strategies [3, 4]. Research continues to explore IE2 as a target for small molecules and other gene-silencing technologies to treat resistant CMV infections [7, 13].

Other names

UL122IE86Major immediate-early protein 2pUL122Regulatory protein IE2

Antisense oligonucleotide-mediated inhibition of translation of the IE2 mRNA, which prevents the synthesis of the IE2 protein and subsequently blocks viral replication [1, 2, 5].