Effect of cyclin-dependent kinase inhibitor p21 on regulating viral lytic replication of human herpesvirus 8

Objective To explore the role of cyclin-dependent kinase inhibitor p21 in regulating the lytic replication of human herpesvirus 8 (KSHV).Methods After pretreatment with the histone deacetylase (HDAC) inhibitor SAHA, the number of red fluorescent protein (RFP)-positive iSLK.219 cells was observed by inverted fluorescence microscopy. The mRNA levels of HHV-8 virus-related genes in TREx-K-Rta BCBL-1 cells were detected by real-time quantitative PCR. After liposomal transfection of p21-siRNA, the expression of p21 protein in iSLK.219 and TREx-K-Rta BCBL-1 cells was detected by Western blot; the percentage of RFP-positive iSLK.219 cells was calculated, and the levels of ORF50 and PAN mRNA in TREx-K-Rta BCBL-1 cells were detected, and the survival of iSLK.219 and TREx-K-Rta BCBL-1 cells were measured by CCK-8 assay and Trypan blue staining.Results SAHA dramatically enhanced the percent of RFP-positive iSLK.219 cells, and the mRNA levels of ORF50, PAN and K8.1, and p21 expression (P<0.05). Knockdown of p21 significantly suppressed the percentage of RFP-positive iSLK.219 cells, and the mRNA levels of ORF50 and PAN (P<0.05), and protected SAHA-mediated cell death in BCBL-1 cells.Conclusions Inhibition of HDAC activity promotes HHV-8 replication through regulating p21.