Abstract
It has been reported that binding of STAT3 protein to the 5′-flanking region of the relaxin gene may result in downregulation of the relaxin expression. There is a Guanine(G)-rich segment located in about 3.8 Kb upstream of the relaxin gene and very close to the STAT3's binding site. In our study, NMR spectroscopy revealed the formation of G-quadruplex by this G-rich strand, and the result was confirmed by ESI mass spectrometry and CD spectroscopy. The theoretical structure of RLX G-quadruplex was constructed and refined by molecular modeling. When this relaxin G-quadruplex was stabilized by berberine(ΔTm = 10°C), a natural alkaloid from a Chinese herb, the gene expression could be up-regulated in a dose-dependent manner which was proved by luciferase assay. This result is different from the general G-quadruplex function that inhibiting the telomere replication or down-regulating many oncogenes expression. Therefore, our study reported a novel G-quadruplex in the relaxin gene and complemented the regulation mechanism about gene expression by G-quadruplexes.
Highlights
Relaxin (RLX), a polypeptide hormone, was first discovered in 1926 by Frederick Hisaw [1]
The main functions of relaxin are associated with female reproductive physiology and in particular connective tissue remodeling in the interpubic symphysis and uterine cervix to facilitate birth [1,2]
Our research found that berberine could stabilize the G-quadruplex resulting in upregulating the expression of the relaxin gene
Summary
Relaxin (RLX), a polypeptide hormone, was first discovered in 1926 by Frederick Hisaw [1]. The ESI-MS spectrum of this DNA solution S1 [methanol:water = 20:100( v/v)] showed that, in Figure 2C, at 100 mM ammonium acetate, the intensities of the complex ion for the G-quadruplex ion with two NH4+, [S1+2NH4+-6H+]42, became the base peak (100%).
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