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. Author manuscript; available in PMC: 2010 Jun 1.
Published in final edited form as: Dev Dyn. 2009 Jun;238(6):1346–1357. doi: 10.1002/dvdy.21920

Figure 5.

Figure 5

Transient whole embryo reporter assays for Mix.3 transcriptional repression activity. Ectopic expression of Mix.3 inhibits the activity of a Xenopus brachyury promoter driving expression of luciferase (Xbraluc). Co-injection of CDK9:cyclin T2 reverses the repression activity of Mix.3 on the Xbraluc reporter and results in a two-fold activation of luciferase activity. The ability of CDK9:cyclin T2 to alleviate the repression of Mix.3 is dependent on the CDK9-interaction domain in Mix.3. Deletion of the CDK9-interaction domain does not affect Mix.3’s ability to repress the brachyury promoter but blocks the opposing activity of co-injection of CDK9:cyclin T2. Co-injection of CDK9:cyclin K also resulted in relief of the repression activity of Mix.3 to control levels (Xbraluc alone) but did not further activate the reporter as CDK9:cyclin T2 did. Mix.3/Cyclin T2, without added CDK9, showed no significant change in Xbraluc activity relative to Mix.3 mRNA injection alone.