The genomic sequences near the mir-23b-27b-24-1 cluster form G-quadruplexes and are selectively bound by the natural alkaloid tetrandrine.
BACKGROUND
Although the microRNAs miR-23b, miR-27b and miR-24 are located in the same cluster, their expressions in various pathological states are not always comparable. By searching the genomic sequence around mir23b-27b-24-1 in rat, we identified three potential G-quadruplex sequences (PQS) which can fold into different types of G-quadruplexes, including parallel or antiparallel. Natural alkaloids, tetrandrine (TET), displayed different binding affinity with the three G-quadruplexes which may potentially regulate the expression of mir23b-27b-24-1 cluster members.


METHODS
Both electrospray ionization mass spectrometry (ESI-MS) and circular dichroism (CD) spectroscopy were utilized to detect the formation of G-quadruplexes. Six small molecules were screened by ESI-MS for their binding affinity with three G-quadruplexes, which were evaluated by their IRavalues.


RESULTS
The results of ESI-MS and CD experiments confirmed the formation of three G-quadruplexes neighboring the mir23b-27b-24-1 cluster; two of them adopted antiparallel G-quadruplexes, another adopted a parallel G-quadruplex. Screening of small molecules by ESI-MS showed tetrandrine had selective binding affinity for the parallel G-quadruplex. G-quadruplex stabilization by tetrandrine was verified by CD variable temperature measurements.


CONCLUSIONS
The gene of the mir23b-27b-24-1 cluster harbors three G-quadruplexes with typical sequences and structures. Tetrandrine had a selective binding affinity to the parallel G-quadruplex and stabilized it significantly. Copyright © 2015 John Wiley & Sons, Ltd.
Department of Cardiology, Institute of Vascular Medicine, Peking University Third Hospital, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides, Ministry of Health and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing, China.
Yanchao
Y
Qi
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University.
Han
H
Chen
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University.
Wei
W
Tan
Department of Cardiology, Institute of Vascular Medicine, Peking University Third Hospital, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides, Ministry of Health and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing, China.
Yanyan
Y
Li
Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University.
Gu
G
Yuan
Department of Cardiology, Institute of Vascular Medicine, Peking University Third Hospital, Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides, Ministry of Health and Beijing Key Laboratory of Cardiovascular Receptors Research, Beijing, China.
Ming
M
Xu