White Spot Syndrome Virus IE1 and WSV056 Modulate the G1/S Transition by Binding to the Host Retinoblastoma Protein

DNA viruses often target cellular proteins to modulate host cell cycles and facilitate viral genome replication. However, whether proliferation of white spot syndrome virus (WSSV) requires regulation of the host cell cycle remains unclear. In the present study, we show that two WSSV paralogs, IE1 and WSV056, can interact with Litopenaeus vannamei retinoblastoma (Rb)-like protein (lv-RBL) through the conserved LxCxE motif. Further investigation revealed that IE1 and WSV056 could also bind to Drosophila retinoblastoma family protein 1 (RBF1) in a manner similar to how they bind to lv-RBL. Using the Drosophila RBF-E2F pathway as a model system, we demonstrated that both IE1 and WSV056 could sequester RBF1 from Drosophila E2F transcription factor 1 (E2F1) and subsequently activate E2F1 to stimulate the G(1)/S transition. Our findings provide the first evidence that WSSV may regulate cell cycle progression by targeting the Rb-E2F pathway.