Transforming growth factor beta promotes complexes between Smad proteins and the CCCTC-binding factor on the H19 imprinting control region chromatin.
Whether signal transduction pathways regulate epigenetic states in response to environmental cues remains poorly understood. We demonstrate here that Smad3, signaling downstream of transforming growth factor beta, interacts with the zinc finger domain of CCCTC-binding factor (CTCF), a nuclear protein known to act as "the master weaver of the genome." This interaction occurs via the Mad homology 1 domain of Smad3. Although Smad2 and Smad4 fail to interact, an alternatively spliced form of Smad2 lacking exon 3 interacts with CTCF. CTCF does not perturb well established transforming growth factor beta gene responses. However, Smads and CTCF co-localize to the H19 imprinting control region (ICR), which emerges as an insulator in cis and regulator of transcription and replication in trans via direct CTCF binding to the ICR. Smad recruitment to the ICR requires intact CTCF binding to this locus. Smad2/3 binding to the ICR requires Smad4, which potentially provides stability to the complex. Because the CTCF-Smad complex is not essential for the chromatin insulator function of the H19 ICR, we propose that it can play a role in chromatin cross-talk organized by the H19 ICR.
Bergström
Rosita
R
Ludwig Institute for Cancer Research, Uppsala University, SE-751 24 Uppsala, Sweden.
Savary
Katia
K
Morén
Anita
A
Guibert
Sylvain
S
Heldin
Carl-Henrik
CH
Ohlsson
Rolf
R
Moustakas
Aristidis
A
D000818:Animals; D000831:Animals, Newborn; D000076246:CCCTC-Binding Factor; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D018392:Genomic Imprinting / Q000235:genetics; D056945:Hep G2 Cells; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics; D008297:Male; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D002843:Chromatin; C000619698:Ctcf protein, mouse; C094335:H19 long non-coding RNA; C513121:IGF2 protein, mouse; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D012097:Repressor Proteins; D051785:Smad Proteins; D051900:Smad3 Protein; D016212:Transforming Growth Factor beta; D007335:Insulin-Like Growth Factor II