Part:BBa_K2295001

CRE (cAMP response element)

Characterization of the CRE Promoter

The cAMP response element-containing promoter (pCRE), which is pH responsive, was characterized in vitro in Jurkat and HEK293T cell lines. For this purpose, the pH of the media had to be adjusted.

Promoter characterization

In order to characterize the CRE promoter, stably transduced HEK293T and Jurkat lines were created expressing eCFP under a minimal promoter with multiple CRE sites. Induction was performed with pH adjusted media. Constitutively expressed mCherry was used as transduction marker. For analysis in HEK293T, PEI transfection of the pH receptor TDAG8, which is not expressed in these cells, was performed. (Ausländer et al., 2014). To generate a high expression by activating the signaling cascade downstream of the receptor, the stable cell lines were induced with forskolin and IBMX. Forskolin activates the cAMP-producing enzyme adenylyl cyclase and IBMX inhibits cAMP-hydrolyzing phosphodiesterases (Bittinger et al., 2004). Fluorescence was measured by flow cytometry after 24 h of treatment (Fig. 1).

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Figure 1: Flow cytometry of hypoxia response element promoter analysis. a) Jurkat cells stably transduced with 4xCRE-pTal:eCFP were incubated 24 h in pH adjusted RPMI 1640. b) The experiment was repeated inducing with Forskolin (10 µM) and IBMX (10 µM). c) and d) HEK293T cells stably transduced with 4xCRE-pTal:eCFP with and without transient TDAG8 were induced similarly to a) and b). Results show the represent the amount of eCFP positive cells c) and the d) mean fluorescence intensity. All data points are mean values of triplicates, error bars represent standard deviation. Significant differences in a) and b) were determined using ANOVA, for c) and d) significant differences were determined using one-tailed student’s t-test (Excel 2017); * p < 0.05, ** p < 0.01, *** p < 0.001, non-significant differences are not marked.

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  COMPATIBLE WITH RFC[25]
• 1000
  COMPATIBLE WITH RFC[1000]