The POU domain factor Skin-1a represses the keratin 14 promoter independent of DNA binding. A possible role for interactions between Skn-1a and CREB-binding protein/p300.
The genes encoding keratin 5 and 14 are highly expressed in the basal cell layer keratinocytes of the epidermis, but both genes are silenced when keratinocytes move into the suprabasal compartment. The POU homeodomain factors Skn-1a and Tst-1, which are expressed in epidermis, may play a role in the suprabasal repression of the keratin 5 and 14 genes because keratin 14 mRNA expression persists in suprabasal cells in Skn-1/Tst-1 double knockout mice. In transfection experiments, both Skn-1a and Tst-1 repress the keratin 14 promoter, with the POU domain being sufficient for repression. The region of the keratin 14 gene sufficient and required for repression by Skn-1a is a 100-base pair sequence lacking POU-binding sites adjacent to the transcription start site. DNA-binding defective mutants of Skn-1a and Tst-1 are as effective at mediating repression as the wild type proteins, suggesting that protein-protein interactions rather than direct DNA binding are important for repression. We also show that CREB-binding protein (CBP)/p300 co-activators are strong activators of keratin 14 gene expression, acting through sequences close to the keratin 14 promoter. Further, CBP interacts directly with the POU domain of Skn-1a, and increasing concentrations of CBP can overcome Skn-1a-mediated repression, suggesting that POU domain factors may repress keratin 14 gene expression by interfering with the activity of co-activators such as CBP/p300.
Sugihara
T M
TM
Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, California 92093-0648, USA.
Kudryavtseva
E I
EI
Kumar
V
V
Horridge
J J
JJ
Andersen
B
B
D000818:Animals; D000831:Animals, Newborn; D020029:Base Pairing; D001665:Binding Sites; D050882:CREB-Binding Protein; D002460:Cell Line; D002478:Cells, Cultured; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D053547:Keratin-14; D053569:Keratin-15; D053555:Keratin-5; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D007633:Keratins / Q000235:genetics*; D008156:Luciferases / Q000235:genetics; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D050816:Octamer Transcription Factor-6; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012867:Skin / Q000166:cytology / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
C507540:KRT14 protein, human; C503940:KRT5 protein, human; D053547:Keratin-14; D053569:Keratin-15; D053555:Keratin-5; C507446:Krt14 protein, mouse; C492053:Krt15 protein, mouse; D009687:Nuclear Proteins; C494178:POU3F1 protein, human; C494180:Pou3f1 protein, mouse; D012333:RNA, Messenger; D011994:Recombinant Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D050816:Octamer Transcription Factor-6; D007633:Keratins; D008156:Luciferases; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494364:Crebbp protein, mouse