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Human NAD(P)H:quinone oxidoreductase2. Gene structure, activity, and tissue-specific expression
1Department of Pharmacology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111.
The Journal of Biological Chemistry
|May 20, 1994
Summary
The human NQO2 gene, a second member of the NQO gene family, shares conserved sequences with NQO1. Its 5'-flanking region contains regulatory elements like ARE and XRE, influencing gene expression.
Area of Science:
- Genetics
- Molecular Biology
- Biochemistry
Background:
- The human NAD(P)H:quinone oxidoreductase2 (NQO2) gene is a newly identified member of the NQO gene family.
- Understanding the NQO2 gene's structure, regulation, and function is crucial for comprehending cellular responses to xenobiotics and oxidative stress.
Purpose of the Study:
- To sequence and characterize the human NQO2 gene, including its flanking regions.
- To investigate the regulatory elements within the NQO2 5'-flanking region.
- To determine the expression pattern and functional activity of the NQO2 gene and its protein product.
Main Methods:
- DNA sequencing of the NQO2 gene and its 5' and 3' flanking regions.
- Comparative sequence analysis with the NQO1 gene.
- Bioinformatic analysis to identify regulatory elements (SP1, ARE, XRE) in the 5'-flanking region.
- Functional assays in COS1 and Hep-G2 cells to assess NQO2 protein activity and promoter function.
- Northern blot analysis to determine tissue-specific gene expression.
Main Results:
- The NQO2 gene comprises seven exons and six introns, with conserved sequences in exons 3-6 compared to NQO1. The NQO2 protein is shorter than NQO1.
- The 5'-flanking region contains SP1, ARE, and XRE binding sites, similar to NQO1.
- NQO2 protein demonstrated nitroreductase activity against an anti-tumor compound.
- NQO2 is expressed in heart, brain, lung, liver, and skeletal muscle, but not in placenta, with variable expression levels.
- The NQO2 5'-flanking region, containing ARE and XRE, enhanced CAT gene expression in response to specific inducers in Hep-G2 cells.
Conclusions:
- The structural and sequence similarities confirm NQO2 as a distinct member of the human NQO gene family.
- The identified regulatory elements suggest NQO2's role in responding to oxidative stress and xenobiotics.
- NQO2 exhibits tissue-specific expression and enzymatic activity, contributing to cellular defense mechanisms.