title: Position effect variegation  and epigenetic modification of a transgene in a pig model.
abstract: Sequences  proximal to transgene integration sites are able to regulate transgene  expression, resulting in complex position effect variegation. Position effect  variegation can cause differences in epigenetic modifications, such as DNA  methylation and histone acetylation. However, it is not known which factor,  position effect or epigenetic modification, plays a more important role in the  regulation of transgene expression. We analyzed transgene expression patterns  and epigenetic modifications of transgenic pigs expressing green fluorescent  protein, driven by the cytomegalovirus (CMV) promoter. DNA hypermethylation and  loss of acetylation of specific histone H3 and H4 lysines, except H4K16  acetylation in the CMV promoter, were consistent with a low level of transgene  expression. Moreover, the degree of DNA methylation and histone H3/H4  acetylation in the promoter region depended on the integration site;  consequently, position effect variegation caused variations in epigenetic  modifications. The transgenic pig fibroblast cell lines were treated with DNA  methyltransferase inhibitor 5-Aza-2'-deoxycytidine and/or histone deacetylase  inhibitor trichostatin A. Transgene expression was promoted by reversing the  DNA hypermethylation and histone hypoacetylation status. The differences in DNA  methylation and histone acetylation in the CMV promoter region in these cell  lines were not significant; however, significant differences in transgene  expression were detected, demonstrating that variegation of transgene  expression is affected by the integration site. We conclude that in this pig  model, position effect variegation affects transgene expression.
authors.affiliation: College of Life Science, Northeast Agricultural University of China, Harbin, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Yin
authors.forename: Q R
authors.initials: QR
authors.lastname: Kong
authors.forename: Z P
authors.initials: ZP
authors.lastname: Zhao
authors.forename: M L
authors.initials: ML
authors.lastname: Wu
authors.forename: Y S
authors.initials: YS
authors.lastname: Mu
authors.forename: K
authors.initials: K
authors.lastname: Hu
authors.forename: Z H
authors.initials: ZH
authors.lastname: Liu
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D042002:Chromatin Assembly and Disassembly; D055012:Chromosomal Position Effects / Q000235:genetics*; D003587:Cytomegalovirus / Q000235:genetics; D019175:DNA Methylation / Q000235:genetics*; D000077209:Decitabine; D004791:Enzyme Inhibitors / Q000494:pharmacology; D014644:Genetic Variation; D049452:Green Fluorescent Proteins / Q000096:biosynthesis* / Q000235:genetics*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006657:Histones / Q000378:metabolism; D006877:Hydroxamic Acids / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D013552:Swine / Q000235:genetics; D019076:Transgenes / Q000235:genetics*
chemical_list: D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D049452:Green Fluorescent Proteins; C012589:trichostatin A; D000077209:Decitabine; D001374:Azacitidine