We also were able to identify an enhancer of the Talon gene. Like all enhancers,
ID: 253726 • Letter: W
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We also were able to identify an enhancer of the Talon gene. Like all enhancers, this DNA sequence increased the expression levels of the Talon gene. The sequence of the Talon enhancer is shown below The Talon gene also is regulated by two Transcription factors named Hippogenin and Grittogenin. These factors bind to the DNA sequences 5'AATT3' (for Hippogenin) and 5 CCCGGG3' (for Griffogenin Underneath the sequence is shown the structures of five enhancer variants: the wild-type enhancer (g) plus four deletion mutants (h through k). Each variant was tested for its ability to help the promoter to increase the transcription of the Talon gene. Relative levels of expression are shown to the right. GATCactivity Relative gene S-AGCTGAGAATTCGCGAT 1000 Units 500 Units 500 Units 10 Units 10 Units 9 b. For each construct (h-k), indicate which transcription factor's ability to bind to the enhancer might be affected, and suggest why the expression level is changed to the extent shown.Explanation / Answer
For h, binding of Hippogenin (which recognizes AATT) is affected. As this transcription factor cannot bind to this region, the gene expression level falls. There are two hippogenin binding sites. As only one is mutated, there is small decrease in gene expression.
For i, binding of Hippogenin is again affected. In this case as the second hippogenin binding site is mutated, the gene expression level drops by the same level as previous case. This is because, in this case the second binding site is still available for binding by hippogenin.
In j, both the hippogenin binding sites are mutated. Hence the gene exression level is drastically effected as hipogenin a transcriptionla factor cannot bind to the promoter seqeunce.
In k, the griffogenin (binds to CCCGGG) site is mutated. As this trasncriptional factor cannot bind to the promoter, a large change in gene expression level is observed.
by looking at the changes is gene expression levels due to mutation we can say that binding of 2 hippogenin and one griffogenin is essential for optimal gene expression.
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