title: Targeted gene suppression by inducing de novo DNA methylation in the gene promoter.
abstract: BACKGROUND
  Targeted gene silencing is an important approach in both drug development and basic research. However, the selection of a potent suppressor has become a significant hurdle to implementing maximal gene inhibition for this approach. We attempted to construct a 'super suppressor' by combining the activities of two suppressors that function through distinct epigenetic mechanisms.
  
  
  RESULTS
  Gene targeting vectors were constructed by fusing a GAL4 DNA-binding domain with a epigenetic suppressor, including CpG DNA methylase Sss1, histone H3 lysine 27 methylase vSET domain, and Kruppel-associated suppression box (KRAB). We found that both Sss1 and KRAB suppressors significantly inhibited the expression of luciferase and copGFP reporter genes. However, the histone H3 lysine 27 methylase vSET did not show significant suppression in this system. Constructs containing both Sss1 and KRAB showed better inhibition than either one alone. In addition, we show that KRAB suppressed gene expression by altering the histone code, but not DNA methylation in the gene promoter. Sss1, on the other hand, not only induced de novo DNA methylation and recruited Heterochromatin Protein 1 (HP1a), but also increased H3K27 and H3K9 methylation in the promoter.
  
  
  CONCLUSIONS
  Epigenetic studies can provide useful data for the selection of suppressors in constructing therapeutic vectors for targeted gene silencing.
authors.affiliation: King's Lab, Shanghai Jiao Tong University School of Pharmacy, 800 Dongchuan Road, Shanghai 200240, China.|Stanford University Medical School, VA Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA.
authors.forename: Ai-Niu
authors.initials: AN
authors.lastname: Ma
authors.affiliation: King's Lab, Shanghai Jiao Tong University School of Pharmacy, 800 Dongchuan Road, Shanghai 200240, China.|Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, 519 Dongminzhu Blvd, Changchun 130021, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: King's Lab, Shanghai Jiao Tong University School of Pharmacy, 800 Dongchuan Road, Shanghai 200240, China.|Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, 519 Dongminzhu Blvd, Changchun 130021, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Guo
authors.affiliation: King's Lab, Shanghai Jiao Tong University School of Pharmacy, 800 Dongchuan Road, Shanghai 200240, China.
authors.forename: Yong-Xiang
authors.initials: YX
authors.lastname: Wang
authors.affiliation: Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, 519 Dongminzhu Blvd, Changchun 130021, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.affiliation: Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, 519 Dongminzhu Blvd, Changchun 130021, China.
authors.forename: Jiuwei
authors.initials: J
authors.lastname: Cui
authors.affiliation: Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, 519 Dongminzhu Blvd, Changchun 130021, China.
authors.forename: Guanjun
authors.initials: G
authors.lastname: Wang
authors.affiliation: Stanford University Medical School, VA Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Hoffman
authors.affiliation: Stem Cell and Cancer Center, First Affiliated Hospital, Jilin University, 519 Dongminzhu Blvd, Changchun 130021, China.|Stanford University Medical School, VA Palo Alto Health Care System, 3801 Miranda Avenue, Palo Alto, CA 94304, USA.
authors.forename: Ji-Fan
authors.initials: JF
authors.lastname: Hu
keywords: DNA methylation; Epigenetics; Gene expression; Gene suppression; H3K27 methylation; Histone code