title: Induction of Transcription Factor Early Growth Response Protein 1 during HSV-1 Infection Promotes Viral Replication in Corneal Cells.
abstract: OBJECTIVE
  To understand the mechanisms of Early Growth Response Protein 1 (Egr-1) induction upon HSV-1 lytic infection and its roles in regulating viral gene expression and replication.
  
  
  METHODS
  Rabbit corneal cell line SIRC and other cell lines were infected by HSV-1 to investigate the Egr-1 induction and its occupancy on the viral genome in different conditions. UV-inactivated HSV-1 and a recombinant virus over-expressing Egr-1 were generated to evaluate the regulatory effects on viral gene expression and replication during the infection.
  
  
  METHODS
  Egr-1 induction triggered by viral infection was determined by Western Blot analyses and immune-fluorescent microscopy. Real-time RT-PCR and a novel Cignal™Reporter Assay were used for quantitative measurement of Egr-1 expression. Chromatin Immuno-precipitation (ChIP) was performed to address the Egr-1 occupancy to the viral regulatory sequences and the influence on viral replication was assessed by plaque assays.
  
  
  RESULTS
  Our results indicated that Egr-1 expression requires viral gene expression since the UV-inactivated HSV-1 failed to produce Egr-1 protein. Blockade of viral replication did not block the Egr-1 protein synthesis, supporting the hypothesis that HSV-1 replication was not essential for Egr-1 production. Chromatin immune-precipitation (ChIP) and RT-PCR assays demonstrated that induced Egr-1 was able to interact with key regulatory elements near HSV-1 immediate-early (IE) genes and promote viral gene expression. Recombinant virus overexpressing Egr-1 revealed that Egr-1 enhanced the viral replication and the release of infectious virus.
  
  
  CONCLUSIONS
  Together these results concluded that HSV-1 triggers the expression of an important host transcription factor Egr-1 via a unique mechanism and benefit the viral gene expression and replication.
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, University of Maryland Eastern Shore, 1 College Backbone Road, Princess Anne, MD 21853, USA.
authors.forename: S C
authors.initials: SC
authors.lastname: Hsia
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, University of Maryland Eastern Shore, 1 College Backbone Road, Princess Anne, MD 21853, USA.
authors.forename: L P
authors.initials: LP
authors.lastname: Graham
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, University of Maryland Eastern Shore, 1 College Backbone Road, Princess Anne, MD 21853, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Bedadala
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, University of Maryland Eastern Shore, 1 College Backbone Road, Princess Anne, MD 21853, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Balish
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, University of Maryland Eastern Shore, 1 College Backbone Road, Princess Anne, MD 21853, USA.
authors.forename: F
authors.initials: F
authors.lastname: Chen
authors.affiliation: Pharmaceutical Sciences, School of Pharmacy, University of Maryland Eastern Shore, 1 College Backbone Road, Princess Anne, MD 21853, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Figliozzi
keywords: Egr-1; HSV-1; corneal cells; lytic infection; viral replication