title: Tethering of the conserved piggyBac transposase fusion protein CSB-PGBD3 to chromosomal AP-1 proteins regulates expression of nearby genes in humans.
abstract: The CSB-PGBD3 fusion protein arose more than 43 million years ago when a 2.5-kb piggyBac 3 (PGBD3) transposon inserted into intron 5 of the Cockayne syndrome Group B (CSB) gene in the common ancestor of all higher primates. As a result, full-length CSB is now coexpressed with an abundant CSB-PGBD3 fusion protein by alternative splicing of CSB exons 1-5 to the PGBD3 transposase. An internal deletion of the piggyBac transposase ORF also gave rise to 889 dispersed, 140-bp MER85 elements that were mobilized in trans by PGBD3 transposase. The CSB-PGBD3 fusion protein binds MER85s in vitro and induces a strong interferon-like innate antiviral immune response when expressed in CSB-null UVSS1KO cells. To explore the connection between DNA binding and gene expression changes induced by CSB-PGBD3, we investigated the genome-wide DNA binding profile of the fusion protein. CSB-PGBD3 binds to 363 MER85 elements in vivo, but these sites do not correlate with gene expression changes induced by the fusion protein. Instead, CSB-PGBD3 is enriched at AP-1, TEAD1, and CTCF motifs, presumably through protein-protein interactions with the cognate transcription factors; moreover, recruitment of CSB-PGBD3 to AP-1 and TEAD1 motifs correlates with nearby genes regulated by CSB-PGBD3 expression in UVSS1KO cells and downregulated by CSB rescue of mutant CS1AN cells. Consistent with these data, the N-terminal CSB domain of the CSB-PGBD3 fusion protein interacts with the AP-1 transcription factor c-Jun and with RNA polymerase II, and a chimeric CSB-LacI construct containing only the N-terminus of CSB upregulates many of the genes induced by CSB-PGBD3. We conclude that the CSB-PGBD3 fusion protein substantially reshapes the transcriptome in CS patient CS1AN and that continued expression of the CSB-PGBD3 fusion protein in the absence of functional CSB may affect the clinical presentation of CS patients by directly altering the transcriptional program.
authors.affiliation: Department of Biochemistry, School of Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Lucas T
authors.initials: LT
authors.lastname: Gray
authors.forename: Kimberly K
authors.initials: KK
authors.lastname: Fong
authors.forename: Thomas
authors.initials: T
authors.lastname: Pavelitz
authors.forename: Alan M
authors.initials: AM
authors.lastname: Weiner
mesh_terms: D001665:Binding Sites; D000076246:CCCTC-Binding Factor; D003057:Cockayne Syndrome / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics; D050506:Mutant Chimeric Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D000075223:Poly-ADP-Ribose Binding Proteins; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D000091262:TEA Domain Transcription Factors; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome
chemical_list: D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D050506:Mutant Chimeric Proteins; D009687:Nuclear Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D012097:Repressor Proteins; D000091262:TEA Domain Transcription Factors; C057182:TEAD1 protein, human; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C574548:CSB-PGBD3 fusion protein, human; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes