Abstract
BackgroundA 39-base-pair sequence (Pu39WT) located 58 to 19 base pairs upstream of the Bcl-2 P1 promoter has been implicated in the formation of an intramolecular mixed G-quadruplex structure and is believed to play a major role in the regulation of bcl-2 transcription. However, an extensive functional exploration requires further investigation. To further exploit the structure–function relationship of the Pu39WT-hemin DNAzyme, the secondary structure and peroxidase activity of the Pu39WT-hemin complex were investigated.ResultsExperimental results showed that when Pu39WT was incubated with hemin, it formed a uniparallel G-quadruplex-hemin complex in K+ or Na+ solution, rather than a mixed hybrid without bound hemin. Also, Pu39WT-hemin showed peroxidase activity (ABTS2−) in the presence of H2O2 to produce the colored radical anion (ABTS•-), which could then be used to determine the parameters governing the catalytic efficiency and reveal the peroxidase activity of the Pu39WT-hemin DNAzyme.ConclusionsThese results demonstrate the general peroxidase activity of Pu39WT-hemin DNAzyme, which is an intramolecular parallel G-quadruplex structure. This peroxidase activity of hemin complexed with the G-quadruplex-forming sequence in the Bcl-2 gene promoter may imply a potential mechanism of hemin-mediated cellular injury.
Highlights
A 39-base-pair sequence (Pu39WT) located 58 to 19 base pairs upstream of the Bcl-2 P1 promoter has been implicated in the formation of an intramolecular mixed G-quadruplex structure and is believed to play a major role in the regulation of bcl-2 transcription
Pu39WT binding hemin formed a uniparallel G-quadruplex structure in K+ and Na+ solutions, rather than a mixed hybrid structure without bound hemin We compared the structural differences between Pu39WT G-quadruplexes in K+ and Na+ solution before and after the addition of hemin (Figure 1)
Once the DNAzyme was formed by Pu39WT binging hemin, it possessed a stable peroxidase activity. These results indicated that Pu39WT-formed Gquadruplex-hemin complexes, in K+ and Na+, possess a stable general peroxidase activity and the intramolecular parallel G-quadruplex structure may be essential for catalysis
Summary
A 39-base-pair sequence (Pu39WT) located 58 to 19 base pairs upstream of the Bcl-2 P1 promoter has been implicated in the formation of an intramolecular mixed G-quadruplex structure and is believed to play a major role in the regulation of bcl-2 transcription. The G-quadruplex-forming region is strongly associated with nuclease hypersensitive sites and plays a major role in the regulation of Bcl-2 transcription, extensive functional exploration is warranted requiring further investigation [4,5]. The activation of caspases is a major player and decoder in the process of controlling apoptosis via the regulation of redox equilibrium relationship of the Pu39WT-hemin DNAzyme, the secondary structure and peroxidase activity of Pu39WT-hemin complex were investigated
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