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Today, a presenter briefly mentioned that gene expression in sea urchins during development might be manipulated using VP16 and engrailed fusions.

On a slide, it said that expression might be increased by mRNA injection or "VP16 fusion to binding domain of TF" and decreased by antisense morpholinos or "engrailed fusion to binding domain of TF".

I understand mRNA injection and antisense morpholinos, but I am unclear about the roles of VP16 and engrailed in this context. Can anyone clarify?

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VP16-activation domain fusion to a DBD can make the hybrid protein get strongly and easily activatable. Check this paper out.. quite an old one – WYSIWYG Apr 12 '13 at 8:35
@WYSIWYG: thanks, that addressed the first part of the question. Apparently, genetic manipulation in sea urchin embryos is quite tricky, so I'm not surprised to see a rather old paper as a reference for a technique. – dd3 Apr 12 '13 at 15:32
And I found the answer to the second part: @WYSIWG, if you want to write your part as an answer, I can add this part and mark the whole question as answered. – dd3 Apr 12 '13 at 15:35 problem.. – WYSIWYG Apr 13 '13 at 6:28
up vote 1 down vote accepted

VP16 is a herpesvirus derived protein transcription factor, which activates the early genes of the viral infection cycle. The activation domain (AD) which is formed by the 78-amino acids from the C-terminal, can be fused to DNA binding domain of other protein transcription factors, such as GAL4, to make a hybrid protein that constitutively and strongly activates transcription, without the requirement of any ligands. VP16-AD interacts with TBP, TFIID, SAGA histone acetyltransferase complex, and PC4 (transcriptional coactivator positive cofactor 4) to drive transcription.

The engrailed gene, from Drosophila, is a transcriptional repressor. When the repressor domain is fused to transcription factors, the fusion results in trans-dominant negative functions of the transcription factor (phenocopying loss of function mutations in the target genes).

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