Recruitment of histone modifications by USF proteins at a vertebrate barrier element.
The chicken beta-globin 5'HS4 insulator element acts as a barrier to the encroachment of chromosomal silencing. Endogenous 5'HS4 sequences are highly enriched with histone acetylation and H3K4 methylation regardless of neighboring gene expression. We report here that 5'HS4 elements recruit these histone modifications when protecting a reporter transgene from chromosomal silencing. Deletion studies identified a single protein binding site within 5'HS4, footprint IV, that is necessary for the recruitment of histone modifications and for barrier activity. We have determined that USF proteins bind to footprint IV. USF1 is present in complexes with histone modifying enzymes in cell extracts, and these enzymes specifically interact with the endogenous 5'HS4 element. Knockdown of USF1 expression leads to a loss of histone modification recruitment and subsequent encroachment of H3K9 methylation. We propose that barrier activity requires the constitutive recruitment of H3K4 methylation and histone acetylation at multiple residues to counteract the propagation of condensed chromatin structures.
West
Adam G
AG
Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA.
Huang
Suming
S
Gaszner
Miklos
M
Litt
Michael D
MD
Felsenfeld
Gary
G
D000107:Acetylation; D000818:Animals; D001483:Base Sequence; D002645:Chickens; D018983:DNA Footprinting; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D020868:Gene Silencing; D017930:Genes, Reporter; D005914:Globins / Q000235:genetics*; D006657:Histones / Q000378:metabolism*; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000502:physiology; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D019076:Transgenes; D051720:Upstream Stimulatory Factors
D004268:DNA-Binding Proteins; D006657:Histones; D015375:Receptors, Interleukin-2; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors; D005914:Globins