Detection of quadruplex DNA structures in human telomeres by a fluorescent carbazole derivative.
Single-stranded telomeric DNA tends to form a four-base-paired planar structure termed G-quadruplex. This structure was easily formed in vitro in the presence of monovalent cations. However, the existence of this structure in native human telomeres is unclear. Here we address this important question through the distinctive properties of 3,6-bis(1-methyl-4-vinylpyridinium)carbazole diiodide (BMVC) upon binding to various DNA structures. Although the fluorescence of BMVC increases significantly in the presence of DNA, BMVC has high sensitivity and binding preference to quadruplex d(T(2)AG(3))(4) over duplex DNA. In addition, the fluorescent emissions were characterized around 575 nm for quadruplex d(T(2)AG(3))(4) and 545 nm for most of duplex DNA. The 575-nm fluorescence emissions were detected in the mixtures of 2 nM BMVC with the chromosomal DNA that were extracted from human cells, suggesting the presence of quadruplex structure in human nucleus. Further analyzing the BMVC fluorescence at the ends of metaphase chromosomes and other regions of chromosomes, we detected the quadruplex-binding BMVC fluorescence at telomere-proximal regions. Together these results provide the first evidence for the presence of quadruplex structures in human telomeres.
Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, 106, Taiwan, Republic of China.
Cheng-Chung
CC
Chang
I-Chun
IC
Kuo
I-Fang
IF
Ling
Chin-Tin
CT
Chen
Huei-Chin
HC
Chen
Pei-Jen
PJ
Lou
Jing-Jer
JJ
Lin
Ta-Chau
TC
Chang
D001665:Binding Sites; D002227:Carbazoles / Q000737:chemistry; D002460:Cell Line; D002467:Cell Nucleus / Q000648:ultrastructure; D004247:DNA / Q000737:chemistry*; D005456:Fluorescent Dyes; D006801:Humans; D008677:Metaphase; D018613:Microscopy, Confocal; D011726:Pyridinium Compounds / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D016615:Telomere / Q000235:genetics* / Q000648:ultrastructure*
C486012:3,6-bis(1-methyl-4-vinylpyridium)carbazole diiodide; D002227:Carbazoles; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D004247:DNA