scholarly journals Differential Activation of the Connexin 43 Promoter by Dimers of Activator Protein-1 Transcription Factors in Myometrial Cells

Endocrinology ◽  
2005 ◽  
Vol 146 (4) ◽  
pp. 2048-2054 ◽  
Author(s):  
Jennifer A. Mitchell ◽  
Stephen J. Lye
Keyword(s):  
Transcription Factors ◽  
Connexin 43 ◽  
Family Members ◽  
Expression Vectors ◽  
Central Component ◽  
Activator Protein 1 ◽  
Cx43 Expression ◽  
Myometrial Cells ◽  
Activator Protein ◽  
Expression Of Genes

Abstract The expression of activator protein-1 (AP-1) transcription factors is increased in the myometrium at term and may therefore regulate the expression of genes, such as connexin 43 (Cx43), required for the onset of labor. The region upstream of the mouse, rat, and human Cx43 genes contains two consensus AP-1 binding sequences, a proximal AP-1, located close to the TATA box, and a distal AP-1, 1 kb upstream. A transient transfection system was developed in which Syrian hamster myometrial cells were transfected with Cx43 promoter-luciferase constructs in combination with expression vectors for the AP-1 family. Transfection with c-Jun or JunB had no effect on transcription from the Cx43 promoter, whereas transfection with JunD or combinations of Jun and Fos family members led to significant increases in transcription. Deletion of the distal AP-1 site did not abrogate transcription driven by Fos/Jun, whereas a 2-bp mutation in the proximal AP-1 site significantly reduced pCx43 transactivation by AP-1 dimers. Dimers comprising Fos/Jun proteins conferred greater transcriptional activity than Jun dimmers, with Fra-2/JunB combination conferring greatest activity. These data suggest that increased expression of Fos family members in the myometrium at term drives the increase in Cx43 transcription and expression during labor. Because expression of Fra-2 increases earlier than other Fos family members and confers the highest transcriptional drive to the Cx43 promoter, our data suggest that Fra-2 is a central component in the regulation of Cx43 expression during labor.

Phorbol ester treatment of human myometrial cells suppresses expression of oxytocin receptor through a mechanism that does not involve activator protein-1

2006 ◽  
Vol 291 (5) ◽  
pp. E922-E928 ◽  
Author(s):  
Allison Ball ◽  
Jing Wei Wang ◽  
Susan Wong ◽  
Barbara Zielnik ◽  
Jana Mitchell ◽  
...  
Keyword(s):  
Phorbol Ester ◽  
Prolonged Exposure ◽  
Late Pregnancy ◽  
Expression Vectors ◽  
Activator Protein 1 ◽  
Adenoviral Infection ◽  
Myometrial Cells ◽  
Activator Protein ◽  
Labor Onset ◽  
G Protein Coupled

Oxytocin (OT) is a potent uterine agonist. Its receptor (OTR) is a G protein-coupled receptor that is downregulated by prolonged exposure to OT. We hypothesized that activation of PKC mediated this OT-induced decrease in OTR expression. Diminished PKC activity in late pregnancy could underlie the increased expression of uterine OTR preceding labor onset. Using cell cultures of transformed human uterine myocytes, we determined the effects of PKC agonists and antagonists on the expression of OTR. We also explored the effects of overexpression of activator protein-1 (AP-1, a mediator of many PKC- and phorbol ester-induced effects) using adenoviral expression vectors for the AP-1 subunits c-Jun and c-Fos. Stimulation of PKC using the phorbol ester 12- O-tetradecanoylphorbol 13-acetate caused a rapid, significant (P ≤ 0.05) increase in c-Jun and c-Fos concentrations but a significant decrease in mRNA for OTR within 6 h followed by a significant decrease in OT binding by 24 h. Adenoviral infection of the cells with expression vectors for c-Jun and c-Fos increased the AP-1 subunits but had no effect on OTR expression. Furthermore, there were no changes in c-Fos or c-Jun levels in human intrauterine tissues around the time of labor onset, as measured by Western analyses. We conclude that phorbol ester treatment decreases OTR expression, likely through a mechanism that does not involve AP-1.

scholarly journals Neisseria gonorrhoeae Epithelial Cell Interaction Leads to the Activation of the Transcription Factors Nuclear Factor κB and Activator Protein 1 and the Induction of Inflammatory Cytokines

1997 ◽  
Vol 186 (2) ◽  
pp. 247-258 ◽  
Author(s):  
Michael Naumann ◽  
Silja Weßler ◽  
Cornelia Bartsch ◽  
Björn Wieland ◽  
Thomas F. Meyer
Keyword(s):  
Transcription Factors ◽  
Epithelial Cells ◽  
Neisseria Gonorrhoeae ◽  
Transcriptional Activation ◽  
Inflammatory Cytokine ◽  
Nuclear Factor ◽  
Activator Protein 1 ◽  
Messenger Rnas ◽  
Basic Leucine Zipper ◽  
Activator Protein

We have studied the effect of human bacterial pathogen Neisseria gonorrhoeae (Ngo) on the activation of nuclear factor (NF)-κB and the transcriptional activation of inflammatory cytokine genes upon infection of epithelial cells. During the course of infection, Ngo, the etiologic agent of gonorrhea, adheres to and penetrates mucosal epithelial cells. In vivo, localized gonococcal infections are often associated with a massive inflammatory response. We observed upregulation of several inflammatory cytokine messenger RNAs (mRNAs) and the release of the proteins in Ngo-infected epithelial cells. Moreover, infection with Ngo induced the formation of a NF-κB DNA–protein complex and, with a delay in time, the activation of activator protein 1, whereas basic leucine zipper transcription factors binding to the cAMP-responsive element or CAAT/enhancer-binding protein DNA-binding sites were not activated. In supershift assays using NF-κB–specific antibodies, we identified a NF-κB p50/p65 heterodimer. The NF-κB complex was formed within 10 min after infection and decreased 90 min after infection. Synthesis of tumor necrosis factor α and interluekin (IL)-1β occurred at later times and therefore did not account for NF-κB activation. An analysis of transiently transfected IL-6 promoter deletion constructs suggests that NF-κB plays a crucial role for the transcriptional activation of the IL-6 promoter upon Ngo infection. Inactivation of NF-κB conferred by the protease inhibitor N-tosyl-l-phenylalanine chloromethyl ketone inhibited mRNA upregulation of most, but not all, studied cyctokine genes. Activation of NF-κB and cytokine mRNA upregulation also occur in Ngo-infected epithelial cells that were treated with cytochalasin D, indicating an extracellular signaling induced before invasion.

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