A CTCF-dependent silencer located in the differentially methylated area may regulate expression of a housekeeping gene overlapping a tissue-specific gene domain.
The tissue-specific chicken alpha-globin gene domain represents one of the paradigms, in terms of its constitutively open chromatin conformation and the location of several regulatory elements within the neighboring housekeeping gene. Here, we show that an 0.2-kb DNA fragment located approximately 4 kb upstream to the chicken alpha-globin gene cluster contains a binding site for the multifunctional protein factor CTCF and possesses silencer activity which depends on CTCF binding, as demonstrated by site-directed mutagenesis of the CTCF recognition sequence. CTCF was found to be associated with this recognition site in erythroid cells but not in lymphoid cells where the site is methylated. A functional promoter directing the transcription of the apparently housekeeping ggPRX gene was found 120 bp from the CTCF-dependent silencer. The data are discussed in terms of the hypothesis that the CTCF-dependent silencer stabilizes the level of ggPRX gene transcription in erythroid cells where the promoter of this gene may be influenced by positive cis-regulatory signals activating alpha-globin gene transcription.
Laboratory of Structural-Functional Organization of Chromosomes, Institute of Gene Biology of the Russian Academy of Sciences, 34/5 Vavilov Street, 117334 Moscow, Russia.
Denis
D
Klochkov
Héctor
H
Rincón-Arano
Elena S
ES
Ioudinkova
Viviana
V
Valadez-Graham
Alexey
A
Gavrilov
Félix
F
Recillas-Targa
Sergey V
SV
Razin
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D000076246:CCCTC-Binding Factor; D002478:Cells, Cultured; D002645:Chickens / Q000235:genetics*; D018899:CpG Islands; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004912:Erythrocytes / Q000502:physiology; D005786:Gene Expression Regulation; D020868:Gene Silencing; D005809:Genes, Regulator / Q000235:genetics; D005914:Globins / Q000235:genetics* / Q000378:metabolism; D008214:Lymphocytes / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D009928:Organ Specificity; D011401:Promoter Regions, Genetic / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*
D000076246:CCCTC-Binding Factor; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D005914:Globins