Nuclear proteins often form punctiform structures, but the precise mechanism for this process is unknown. As a preliminary study, we investigated the aggregation of an HSV-1 immediate-early protein, infected-cell protein 22 （ICP22）, in the nucleus by observing the localization of ICP22-EGFP fusion protein Results showed that, in high-level expression conditions, ICP22-EGFP gradually concentrates in the nucleus, persists throughout the cell cycle without disaggregation even in the cell division phase, and is finally distributed to daughter cells. We subsequently constructed a mammalian cell expression system, which had tetracycline- dependent transcriptional regulators. Consequently, the location of ICP22-EGFP in the nucleus changed with distinct induction conditions. This suggests that the cellular location of ICP22 is also influenced by promoter regulation, in addition to its own structure. Our findings provide new clues for the investigation of transcriptional regulation of viral genes. In addition, the non-protease reporter system we constructed could be utilized to evaluate the role of intemal ribosome entry sites （IRES） on transcriptional regulation.
Wei CUN Jie CHEN Ying ZHANG Long-ding LIU Qi-han LI
The herpes simplex virus type 1 (HSV-1) tegument proteins have important functions in the viral repli- cation process. In order to investigate the role of the HSV-1 tegument protein VP22 in viral replication, its transcriptional regulation of viral promoters was investigated using the chloramphenicol acetyl- transferase (CAT) assay. The results indicate that VP22 exerts a dose-dependent transcriptional in- hibitory effect on the HSV-1 α4, TK, and gC gene promoters. VP22 had the capacity to repress tran- scriptional activation of promoters via different viral transcription regulatory factors such as VP16 and ICP0, as evidenced by the specific repression of the TK and gC gene promoters by ICP0. In addition, VP22 was capable of inhibiting the promotion of ICP0 transcriptional activation in the presence of HAT PCAF, which is even more remarkable than the VP22 repression of ICP0 transcriptional activation. Fi- nally, the transcriptional inhibitory effect of VP22 on other viral promoters was demonstrated by the analysis of β-galactosidase activities in internal controls.
YU Xian1,2, LI WeiZhong1, LIU LongDing1, CHE YanChun1, CUN Wei1, WU WenJuan1, HE ChunYan1, SHAO CongWen1 & LI QiHan1 1 Department of Viral Immunology, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming 650118, China
The molecular modifications of Herpes Simplex Virus Type I （HSV-1） proteins represented by acetylation and phosphorylation are essential to its biological functions. The cellular chromatin-remodeling/ assembly is involved in HSV-1 associated gene transcriptional regulation in human cells harboring HSV-1 lytic or latent infections. Further investigation on these biological events would provide a better understanding of the mechanisms of HSV-1 viral gene transcriptional regulation
An interaction between the HSV-1 UL25 capsid protein and cellular microtubule-associated protein was found using a yeast two-hybrid screen and β-D-galactosidase activity assays. Immunofluorescence microscopy of the UL25 protein demonstrated its co-localization with cellular microtubule-associated protein in the plasma membrane. Further investigations with deletion mutants suggest that UL25 is likely to have a function in the nucleus.
Lei GUO Ying ZHANG Yan-chun CHE Wen-juan WU Wei-zhong LI Li-chun WANG Yun LIAO Long-ding LIU Qi-han LI
Herpes simplex virus (HSV) is a group of common human pathogens with two serotypes HSV-1 and HSV-2.The prevalence of HSV is worldwide.It primarily infects humans through epithelial cells,when it introduces a latent infection into the nervous system.During viral latency,only a region known as the latency-associated transcript (LAT) is expressed.The discovery of HSV miRNAs helps to draw a larger picture of the infection and pathogenesis of the virus.This review summarizes miRNAs found in HSV-1 and HSV-2 so far.The functional studies of miRNAs in HSV to date indicate that they play a stage-specific role coordinated with viral proteins to maintain the virus life cycle.
Viral microRNAs are one component of the RNA interference phenomenon generated during viral infection. They were first identified in the Herpesviridae family, where they were found to regulate viral mRNA translation. In addition, prior work has suggested that Kaposi＇s sarcoma-associated herpesvirus （KSHV） is capable of regulating cellular gene transcription by miRNA. We demonstrate that a miRNA, hsvl-mir-H27, encoded within the genome of herpes simplex virus 1 （HSV-1）, targets the mRNA of the cellular transcriptional repressor Kelch-like 24 （KLHL24） that inhibits transcriptional efficiency of viral imme- diate-early and early genes. The viral miRNA is able to block the expression of KLHL24 in cells infected by HSV-1. Our dis- covery reveals an effective viral strategy for evading host cell defenses and supporting the efficient replication and prolifera- tion of HSV- 1.
