G<sub>2</sub>-quadruplex in the 3’UTR of IE180 regulates Pseudorabies virus replication by enhancing gene expression
Yashu Zhang, Sisi Liu, Hui Jiang, Hui Deng, Dong Chen, Wei Shen, Haifeng Chen, Chao Gao, Shaobo Xiao, Zheng‐Fei Liu, Dengguo Wei
Abstract
RNA secondary structure elements in the mRNA 3ʹ-untranslated regions (3ʹUTR) play important roles in post-transcriptional regulation. RNA structure elements in the viral RNA provide valuable model for studying diverse regulation mechanisms. Herpesvirus genomes are double-stranded DNA with GC-rich sequences, which can be transcribed into abundant GC-rich RNAs. It is valuable to explore the structures and function of those GC-rich RNAs. We identified a G2-quadruplex-forming sequence named PQS18-1 in the 3ʹUTR of the unique immediate early gene of Pseudorabies virus (PRV), an important member of Alphaherpesvirinae subfamily. The RNA PQS18-1 was folded into parallel G-quadruplex structure, enhancing gene expression. Both non-G-quadruplex mutant and G3-quadruplex mutant in the 3ʹUTR showed lower gene expression level than the wildtype G2-quadruplex. TMPyP4 destroyed PQS18-1 G2-quadruplex and suppressed gene expression, accordingly reducing PRV replication by one titre in the PK15 cells at 24 h post infection. Our findings indicated that the RNA G2-quadruplex in 3ʹUTR was essential for high expression of IE180 gene, and it could be a specific post-transcription regulation element in response to small molecules or other macromolecules. This study discovers a novel RNA G2-quadruplex in the 3ʹUTR of an immediate early gene of alphaherpesvirus and provides a new nucleic acid target for anti-virus drug design.