scholarly journals A PIT-1 Homeodomain Mutant Blocks the Intranuclear Recruitment Of the CCAAT/Enhancer Binding Protein α Required for Prolactin Gene Transcription

2003 ◽  
Vol 17 (2) ◽  
pp. 209-222 ◽  
Author(s):  
John F. Enwright ◽  
Margaret A. Kawecki-Crook ◽  
Ty C. Voss ◽  
Fred Schaufele ◽  
Richard N. Day
Keyword(s):  
Gene Transcription ◽  
Binding Protein ◽  
Hormone Deficiency ◽  
Centromeric Heterochromatin ◽  
Pituitary Hormone ◽  
Homeodomain Protein ◽  
Pituitary Cells ◽  
Enhancer Binding Protein ◽  
Ccaat Enhancer Binding Protein ◽  
Prl Gene

Abstract The pituitary-specific homeodomain protein Pit-1 cooperates with other transcription factors, including CCAAT/enhancer binding protein α (C/EBPα), in the regulation of pituitary lactotrope gene transcription. Here, we correlate cooperative activation of prolactin (PRL) gene transcription by Pit-1 and C/EBPα with changes in the subnuclear localization of these factors in living pituitary cells. Transiently expressed C/EBPα induced PRL gene transcription in pituitary GHFT1–5 cells, whereas the coexpression of Pit-1 and C/EBPα in HeLa cells demonstrated their cooperativity at the PRL promoter. Individually expressed Pit-1 or C/EBPα, fused to color variants of fluorescent proteins, occupied different subnuclear compartments in living pituitary cells. When coexpressed, Pit-1 recruited C/EBPα from regions of transcriptionally quiescent centromeric heterochromatin to the nuclear regions occupied by Pit-1. The homeodomain region of Pit-1 was necessary for the recruitment of C/EBPα. A point mutation in the Pit-1 homeodomain associated with the syndrome of combined pituitary hormone deficiency in humans also failed to recruit C/EBPα. This Pit-1 mutant functioned as a dominant inhibitor of PRL gene transcription and, instead of recruiting C/EBPα, was itself recruited by C/EBPα to centromeric heterochromatin. Together our results suggest that the intranuclear positioning of these factors determines whether they activate or silence PRL promoter activity.

scholarly journals Transcriptional Regulation of Cyclooxygenase-2 in Response to Proteasome Inhibitors Involves Reactive Oxygen Species-mediated Signaling Pathway and Recruitment of CCAAT/Enhancer-binding Protein δ and CREB-binding Protein

2005 ◽  
Vol 16 (12) ◽  
pp. 5579-5591 ◽  
Author(s):  
Jun-Jie Chen ◽  
Wei-Chien Huang ◽  
Ching-Chow Chen
Keyword(s):  
Reactive Oxygen Species ◽  
Gene Transcription ◽  
Binding Protein ◽  
Proteasome Inhibitors ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Creb Binding Protein ◽  
Enhancer Binding Protein ◽  
Ccaat Enhancer Binding Protein ◽  
Cox 2

Inhibition of ubiquitin-proteasome pathway has been shown to be a promising strategy for the treatment of inflammation and cancer. Here, we show that proteasome inhibitors MG132, PSI-1, and lactacystin induce COX-2 expression via enhancing gene transcription rather than preventing protein degradation in the human alveolar NCI-H292 and A549, and gastric AGS epithelial cells. NF-IL6 and CRE, but not NF-κB elements on the COX-2 promoter were involved in the gene transcription event. The binding of CCAAT/enhancer binding protein (C/EBP)β and C/EBPδ to the CRE and NF-IL6 elements, as well as the recruitment of CBP and the enhancement of histone H3 and H4 acetylation on the COX-2 promoter was enhanced by MG132. However, it did not affect the total protein levels of C/EBPβ and C/EBPδ. MG132-induced DNA-binding activity of C/EBPδ, but not C/EBPβ was regulated by p38, PI3K, Src, and protein kinase C. Small interfering RNA of C/EBPδ suppressed COX-2 expression, further strengthening the role of C/EBPδ in COX-2 gene transcription. In addition, the generation of intracellular reactive oxygen species (ROS) in response to MG132 contributed to the activation of MAPKs and Akt. These findings reveal that the induction of COX-2 transcription induced by proteasome inhibitors requires ROS-dependent protein kinases activation and the subsequent recruitments of C/EBPδ and CBP.

scholarly journals Cooperative Effects of STAT5 (Signal Transducer and Activator of Transcription 5) and C/EBP β (CCAAT/Enhancer-Binding Protein-β) onβ -Casein Gene Transcription Are Mediated by the Glucocorticoid Receptor

2001 ◽  
Vol 15 (2) ◽  
pp. 228-240 ◽  
Author(s):  
Shannon L. Wyszomierski ◽  
Jeffrey M. Rosen
Keyword(s):  
Transcription Factors ◽  
Glucocorticoid Receptor ◽  
Gene Transcription ◽  
Binding Protein ◽  
Transactivation Domain ◽  
Signal Transducer ◽  
Casein Gene ◽  
Amino Terminal ◽  
Enhancer Binding Protein ◽  
Ccaat Enhancer Binding Protein

Abstract β-Casein gene transcription is controlled primarily by a composite response element (CoRE) that integrates signaling from the lactogenic hormones, PRL, insulin, and hydrocortisone, in mammary epithelial cells. This CoRE contains binding sites for STAT5 (signal transducer and activator of transcription 5) and C/EBPβ (CCAAT/enhancer-binding protein-β) and several half-sites for glucocorticoid receptor (GR). To examine how interactions among these three transcription factors might regulateβ -casein gene transcription, a COS cell reconstitution system was employed. Cooperative transactivation was observed when all three factors were expressed, but unexpectedly was not seen between STAT5 and C/EBPβ in the absence of full-length, transcriptionally active GR. Cooperativity required the amino-terminal transactivation domain of C/EBPβ, and neither C/EBPα nor C/EBPδ was able to substitute for C/EBPβ when cotransfected with STAT5 and GR. Different GR determinants were needed for transcriptional cooperation between STAT5 and GR as compared with those required for all three transcription factors. These studies provide some new insights into the mechanisms responsible for high level, tissue-specific expression conferred by theβ -casein CoRE.

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