Introduction

Promoter deletion analysis combined with luciferase reporter assays is a widely used approach to dissect the regulatory architecture of gene promoters. By creating sequential deletions within a promoter and measuring the resulting transcriptional activity, researchers can identify regions that act as positive regulatory elements (enhancers or activators) or negative regulatory elements (repressors). This method provides critical insight into gene expression control mechanisms.

How Promoter Deletion and Luciferase Assays Work

In this approach, different fragments of a promoter are cloned upstream of a luciferase reporter gene. Each construct contains a specific deletion of the promoter region. When transfected into cells, the luciferase activity reflects the promoter’s ability to drive gene expression.

• A decrease in luciferase activity upon deletion indicates that the removed region contained a positive regulatory element (activator/enhancer).

• An increase in luciferase activity upon deletion suggests that the deleted region had a negative regulatory element (repressor).

Interpreting Deletion Constructs A to D

In the given study, four 150 bp deletion constructs (A, B, C, D) were tested for promoter activity via luciferase assay. The observed activities help identify which regions harbor positive or negative regulatory elements.

• If deletion of a region (e.g., construct B) increases promoter activity compared to the full-length promoter, this region likely contains a negative regulatory element.

• If deletion of a region (e.g., construct A or C) decreases promoter activity, this region likely contains a positive regulatory element.

Choosing the Correct Combination

Based on typical promoter deletion analysis logic:

• Region A likely contains a positive regulatory element if its deletion reduces activity.

• Region B likely contains a negative regulatory element if its deletion increases activity.

• Regions C and D may also contain regulatory elements, but the best-supported combination from the options is A (positive) and B (negative).

Conclusion

Promoter deletion analysis using luciferase reporter assays effectively maps positive and negative regulatory elements. In this case, the best interpretation is that region A contains a positive regulatory element, while region B contains a negative regulatory element. This understanding aids in further functional characterization of gene regulation.

Answer:
The best correct combination indicating positive and negative regulatory elements is (4) A and B.