Instant Access to the Journals you Need

Read Online + Print Articles, for just $40 a month.

Start Your Free Trial

Unexpected Induction of the Human Connexin 43 Promoter by the Ras Signaling Pathway Is Mediated by a Novel Putative Promoter Sequence

Unexpected Induction of the Human Connexin 43 Promoter by the Ras Signaling Pathway Is Mediated by a Novel Putative Promoter Sequence

Abstract

Abstract Connexin 43 (Cx43) is essential for survival and is tightly regulated at the transcriptional and post-transcriptional levels. A number of previous studies have demonstrated altered expression in malignant tissues, and in the presence of carcinogenic factors. We examined the effect of protooncogenes of Cx43 expression, and found no effect on Cx43 promoter activity in cells transformed with Src or erbB2. On the other hand, we identified and characterized a novel sequence that mediates Cx43 promoter regulation in cell lines engineered to overexpress H-Ras. Compared with wild-type NIH3T3 cells, both Cx43 mRNA and protein levels are increased in NIH3T3-Ras cells. The H-Ras+ cells also have enhanced Cx43 promoter activation, which is inhibited by the MEK1 inhibitor 2′-amino-3′-methoxyflavone (PD98059), suggesting that Ras-mediated Cx43 overexpression is via the mitogen activated protein kinase kinase/extracellular signal-regulated pathway. Deletion analysis of the Cx43 promoter revealed a 200-bp region downstream of the Cx43 transcription start site as the minimal sequence essential for the Ras-mediated Cx43 up-regulation. Using this 200-base pair fragment in electrophoretic mobility shift assays, we identified one main protein complex that binds efficiently and is more abundant in nuclear extracts from NIH3T3-Ras and MCF7-Ras cells compared with their matched controls. This complex selectively recognizes a consensus sequence, AGTTCAATCA, located at positions +149 to +158 of the Cx43 promoter. Supershift assays identified the 90-kDa heat shock protein (HSP90) and c-Myc as constituents of this DNA-binding complex. Treatment of cells with the HSP90 inhibitor geldanamycin resulted in repression of the Cx43 promoter activity, and inhibits binding of the complex to the Cx43 promoter. Coimmunoprecipitation studies confirmed the interaction between endogenous HSP90 and c-Myc. This study provides evidence that the transcriptional up-regulation of Cx43 by Ras-Raf-MAPK is mediated via the interaction of a novel Cx43 promoter element with a protein complex that contains both HSP90 and c-Myc.
Loading next page...
 
/lp/am-soc-for-pharma-experimental-therapeutics/unexpected-induction-of-the-human-connexin-43-promoter-by-the-ras-0ffO0qHfNd

You're reading a free preview. Subscribe to read or print the entire article.

And millions more from thousands of peer-reviewed journals, for just $40/month.

Start Your Free Trial

What content is in DeepDyve?

  • Read and share from thousands of the leading scholarly journals from Springer, Elsevier, Nature, IEEE, Wiley-Blackwell and more.
  • All the latest content is available, no embargo periods.

Rent Scholarly Articles?

  • Read the full article in your browser.
  • Each month you can print 20 pages for free.
  • Access all of your rentals from the cloud anywhere you have an internet connection.
  • Beautiful reading experience – Full charts and figures, just like the PDF.
  • Read as much as you'd like - whenever you'd like.

Happy Users

“In one word renting from DeepDyve is FANTASTIC!!! ... 99% of the time I only need access to an article for a month or so, so renting the articles is perfect for me.”

Adam S.

“Thanks for a great service! For an unaffiliated science blogger like myself this is like a dream come true.”

Seppo P.

“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”

Daniel C.

“Let me seize this opportunity and congratulate you on the service you are rendering to the scientific community.”

Joao B.