- Deletion analysis of a promoter region of a gene was carried out to identify the regulatory elements in it. In the figure below, the filled boxes denote the areas of deletion and the observed activities (in arbitrary units) of the promoter are as shown.Based on the observations, following statements were made:
F. The region between-100 and -50 houses a positive regulatory element.
G. The region between -200 and -250 houses a negative regulatory element
H. The region between -150 and -200 houses a positive regulatory element.
Which one of the following options represents the correct interpretation of the data?
(1) Both A and B (2) A only
(3) B only (4) Both B and C
Introduction
Promoter deletion analysis is a fundamental technique used to identify regulatory elements within gene promoters. By systematically deleting segments of the promoter and measuring the resulting transcriptional activity, researchers can infer the presence of positive (activator) or negative (repressor) regulatory elements. In this context, the correct interpretation of data is crucial. Here, we explain why the region between -200 and -250 is identified as a negative regulatory element based on observed promoter activity changes, and why other regions are less likely to house positive regulatory elements.
Basics of Promoter Deletion Analysis
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Positive regulatory elements enhance transcription. Deleting these regions typically decreases promoter activity.
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Negative regulatory elements repress transcription. Deleting these regions typically increases promoter activity.
By comparing promoter activity levels before and after deletion of specific regions, one can deduce the function of those regions.
Why the Region Between -200 and -250 Is a Negative Regulatory Element
In the deletion analysis described:
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Deleting the region between -200 and -250 results in an increase in promoter activity.
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This suggests that the deleted region normally acts to suppress transcription.
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Therefore, this region is classified as a negative regulatory element or repressor site.
Why Regions Between -100 and -50 or -150 and -200 Are Not Positive Regulatory Elements Here
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If the deletion of the -100 to -50 region had removed a positive regulatory element, promoter activity would decrease. However, the data do not show such a decrease, indicating no positive element here.
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Similarly, deletion of the -150 to -200 region does not lead to decreased activity, so it is unlikely to contain a positive regulatory element.
Summary of Interpretation
| Region | Effect of Deletion on Promoter Activity | Interpretation |
|---|---|---|
| -100 to -50 | No significant decrease | No positive regulatory element |
| -150 to -200 | No significant decrease | No positive regulatory element |
| -200 to -250 | Increase | Negative regulatory element |
Conclusion
The correct interpretation of the promoter deletion data is that only the region between -200 and -250 houses a negative regulatory element. This explains why the correct answer is option (3) B only. The other regions do not show evidence of positive regulatory elements based on the promoter activity changes observed.
