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紫玉兰素A与人端粒G-四链体相互作用的光谱学研究;第一个木脂素类衍生物与G-四链体相互作用(英文)



全 文 :第3 6卷,第3期             光 谱 学 与 光 谱 分 析 Vol.36,No.3,pp896-902
2 0 1 6年3月             Spectroscopy and Spectral Analysis  March,2016  
Spectral Analysis of Interaction between Human Telomeric
G-Quadruplex and Liliflorin A,the First Lignan
Derivative Interacted with G-Quadruplex DNA
LIU Ting-ting1,ZHOU Shuang1,JIA Qian-lan1,WANG Wen-shu1,2*,
YAN Xiao-qian1,ZHANG Wen-hao3,WANG Shuai-qi 1,JIAO Yu-guo1
1.Colege of Life and Environmental Sciences,Minzu University of China,Beijing 100081,China            
2.Beijing Engineering Research Center of Food Environment and Health,Minzu University of China,Beijing 100081,China
3.Center of Biomedical Analysis,Tsinghua University,Beijing 100084,China
Abstract Human telomeric G-quadruplex is a four-stranded structure folded by guanines(G)via Hoogsteen
hydrogen bonding.The ligands which stabilize the G-quadruplex are often telomerase inhibitors and may be-
come antitumor agents.Here,the interaction between a lignan derivative liliflorin A and human telomeric se-
quence dGGG(TTAGGG)3G-quadruplex HTG21were examined by CD,FRET,and NMR spectroscopic
methods.In addition,Molecular Docking was used to study the binding of liliflorin A to dTAGGG
(TTAGGG)3G-quadruplex HTG23.The CD data showed that liliflorin A enhanced HTG21 Tm.The Tmvalue
of G-quadruplex was enhanced 3.2℃by 4.0μmol·L
-1 liliflorin A in FRET.The NMR spectra of HTG21
showed vivid alteration after reacting with liliflorin A in 3hours.Molecular Docking suggested liliflorin A
bound to the wide groove of HTG23at G9,G10,G16and G17.Liliflorin A was the first lignan derivative that
could stabilize HTG21selectively and provided a new candidate for antitumor drug design targeting on human
telomeric G-quadruplex.
Keywords Liliflorin A;G-quadruplex;Human telomere;Spectral analysis;Interaction
中图分类号:O657.3  文献标识码:A   DOI:10.3964/j.issn.1000-0593(2016)03-0896-07
 Received:2015-05-08;accepted:2015-11-02
 Foundation item:The National Natural Science Foundation of China(31200260),The First-class University and the First-rate Discipline Con-
struction Projects of Minzu University of China(YLDX01013,2015MDTD08C),together with 111Project(B08044),The
National Colege Students’innovation and entrepreneurship training program(GCCX 2014110017,GCCX 2015110012)
 Biography:LIU Ting-ting,(1987—),Doctoral Candidate of Colege Life and Environmental Sciences,Minzu University of China
e-mail:liutingting1204@163.com  *Corresponding author  e-mail:wangws@muc.edu.cn
Introduction
  In the process of screening bioactive compounds,spectral
analysis could give straightforward,vivid and sensitive infor-
mation for chemical reactions between ligand and biomacro-
molecule which makes the screening fast and efficiently.Gua-
nine-rich DNA sequences in vivo,such as telomeric DNA se-
quence Tel21,Tel26and oncogene promoter regions(c-myc,
bcl-2,or c-kit),can form G-quadruplex via Hoogsteen hydro-
gen bonding,which plays an important role in many signifi-
cant bioprocesses[1].Telomerase is a cancer-specific reverse
transcriptase activated in 80% ~90% of tumors,and ex-
pressed in very low levels or almost undetectable in normal
cels[2].It is reported that when telomeric DNA sequence
formed G-quadruplex,it becomes insensitive to the elongation
by the telomerase,which is a significant biological process for
cels to proliferate[3].Thus,ligands binding to and stabilizing
telomeric G-quadruplex could inhibit the activity of telomerase
and induce apoptosis of tumors[4].
However,the low selectivity of the reported ligands over
duplex DNA and other DNA folded structures lead to their
various bioactivities and inevitable side effects,when they
were evaluated as antitumor leads.Accordingly,screening
new ligands with high selectivity on human telomeric G-quad-
ruplex is deemed to be an attractive tactic for developing effec-
tive antitumor leads[5].
In our previous research,a new lignan named liliflorin A
was extracted from Magnolia liliflora Desr.(Magnoliace-
ae),and it relieved DNA damages induced by UVB irradiation
in rat lymphocyte cels in SCGE assay[6].It is reported that
UVB-irradiation may cause a selective excitation of guanine
folowed by its oxidative decomposition in the telomeric struc-
ture[7].Thus,it is deduced by us that liliflorin A might inter-
act with G-quadruplex in the telomeric structure,leading to
its protective effect in SCGE,which is the motivation of our
present study.Herein,due to their sensitivity and efficiency,
CD spectra were carried out to investigate whether liliflorin A
could stabilize human telomeric G-quadruplex: HTG21
{dGGG(TTAGGG)3}.Furthermore,a series of FRET were
recorded to examine the selective binding toward HTG21,the
results of which were confirmed by NMR experiments.Final-
ly,Docking was performed to check how and where liliflorin
A could interact with HTG23{dTAGGG(TTAGGG)3}as a
confirmation of the spectral analysis.As a result,liliflorin A
is the first lignan isolated from plants which can stabilize
HTG21selectively,compared with not only the hairpin loop
structure nucleotide F10T,but also the two G-quadruplex
formed by oncogene promoter regions sequences c-myc and c-
kit.It is a good candidate for antitumor drug design targeting
human telomeric G-quadruplex.
1 Materials and methods
1.1 Reagents
DNA(HTG21:5’-G3(T2AG3)3-3’;F21T:5’-FAM-
G3(T2AG3)3-TAMRA-3’;c-myc 2345:5’-TGAG3TG4-
AG3TG4A2-3’;F-myc-T:5’-FAM-GAG3TG4AG3TG4A2G-
TAMRA-3’;c-kit:5’-AG3AG3CGCTG3AG2AG3-3’;F-
kit1:5’-FAM-G3AG3CGCTG3AG2AG3-TAMRA-3’;ds26:
5’-CA2TCG2ATCGA2T2CGATC2GAT2G-3’;F10T:5’-
FAM-TATAGCTATA-HEG-TATAGCTATA-TAMRA-3’)
were purchased from Shanghai Sangon Biotechnology Co.
(Shanghai,China),purified by PAGE.
Liliflorin A was abstracted from Magnolia liliiflora
Desr.in our laboratory[6].Berberine and Quercetin were ob-
tained from National Institute for Food and Drug Control
(Beijing,China)and were used without further purification.
Deuteriumoxide (D2O)was obtained from Sigma-Aldrich
Chemical Co.(Germany).Dimethyl sulfoxide(DMSO)was
purchased from Sigma Co.(USA).KCl,NaCl,KH2PO4and
K2HPO4were of al analytical reagent grades purchased from
Beijing Chem.Co.Tris was purchased from Cambridge Iso-
tope Laboratories,Inc.
1.2 Sample preparation
Liliflorin A,Berberine and Quercetin were initialy dis-
solved as a 50.0μmol·L
-1 stock solution in DMSO.The oli-
gomer DNA was heated at 95.0℃for 5minutes,then slowly
cooled to room temperature,and incubated at 4.0 ℃for 6
hours at least.The ligand-DNA complex were formed by
adding smal aliquots of compound from 50.0μmol·L
-1 so-
lution into the DNA samples in CD and FRET experiments.
The solution was equilibrated at room temperature for 24.0
hours before measurements.Final analysis of the CD and
FRET data were carried out by Origin 8.0 (OriginLab
Corp.).
1.3 CD experiments
The oligomer DNA(HTG21)at a final concentration of
5.0μmol·L
-1 was diluted in 10.0mmol·L-1 Tris-HCl
buffer(containing 100.0mmol·L-1 NaCl,pH 7.4)to be
tested by CD experiments.Experiment was performed at 25.0
℃using a Pistarπ-180spectropolarimeter.The scan of the
buffer alone was used as the background,which was subtrac-
ted from the average scan for each sample.A quartz cuvette
with 4mm path length was used for the spectra recorded over
a wavelength range of 230~450at 1nm bandwidth,1nm
step size,and 0.5stime per point.The CD spectrum data
were obtained from 230to 450nm[8].CD-melting experi-
ments were taken at 295nm and at intervals of 5.0℃ over
the range 10.0~90.0℃,with a constant temperature being
maintained for 1sprior to each reading to ensure a stable val-
ue[9].The final data were the average of three measurements.
1.4 FRET experiments
Fluorescence melting curves were determined using a re-
al-time PCR machine(MYIQ2,Bio-rad,USA),with 0.2
μmol·L
-1 of labeled oligomer DNA (F21T,F10T,F-myc-
T,F-kit1)in the 10.0mmol·L-1 Tris-HCl buffer(pH 7.4)
containing 60.0mmol·L-1 KCl of a total reaction volume of
20μL.Fluorescence readings with excitation at 470nm and
detection at 530nm were taken at intervals of 1.0℃over the
range 37.0~99.0 ℃,with a constant temperature being
maintained for 30sprior to each reading to ensure a stable
value[9].As the competitor,a series of double-stranded
(ds26)concentration was used by a competitive FRET-melt-
ing experiment.
1.5 NMR experiments
The oligonucleotides(HTG21,c-myc 2345and c-kit)
were dissolved in 80% phosphate buffer solution (20.0
mmol·L-1 KH2PO4/K2HPO4,70.0mmol·L-1 KCl,90%
H2O/10% D2O,pH 7.4)and 20% DMSO-d6.The known
concentration of(0.01mmol·L-1)Dimethyl-2-silapentane-
5-sulfonate(DSS)was used as internal reference.The con-
798第3期                    光谱学与光谱分析
centrations of each G-quadruplex recorded in the NMR sam-
ples were 1.0mmol·L-1.As the NMR experiments required
relatively high concentration of compounds (1.0 mmol·
L-1),but the compounds were insoluble in water at such high
concentration,thus,20% DMSO has been added to enhance
the solubility of the compound.Liliflorin A was first dis-
solved in DMSO-d6as 200.0mmol·L-1 stock solution.The
ligand-quadruplex complex was formed by adding smal ali-
quots of compound from 200.0mmol·L-1 solution into the
G-quadruplex samples(HTG21,c-myc 2345and c-kit).The
molar ratio of[ligand]/[G-quadruplex]was 1∶1in the NMR
experiments.The solution was equilibrated at room tempera-
ture for 24hours before measurements.1 H-NMR spectra of
the ligand-quadruplex complex were recorded every one hour.
NMR experiments were performed on a Bruker
AVANCE 600spectrometer equipped with a 5mm BBI probe
capable of delivering z-field gradients.The 1 H-NMR spectra
were recorded by the standard Bruker pulse program p3919gp
that applies 3-9-19pulses with gradients for water suppres-
sion,2.0srelaxation delay,64Kdata points,16ppm spec-
trum width,128scans.Al NMR experiments were carried
out at 298K.
1.6 Docking experiments
Calculations were carried out using DockingServer(ht-
tp://www.dockingserver.com).Gasteiger partial charges
were added to the ligand atoms.Non-polar hydrogen atoms
were merged,and rotatable bonds were defined.Docking cal-
culations were carried out on untitled protein model.Essential
hydrogen atoms,Kolman united atom type charges,and sol-
vation parameters were added with the aid of AutoDock
tools[10].The crystal structure of the telomeric G-quadruplex
(PDB ID 2JSM)HTG23was used as an initial model to study
the interaction between the liliflorin A and telomeric DNA.
Ligand structures were constructed in Chemdraw.
2 Results and discussion
2.1 Liliflorin A stable human telomeric G-quadruplex
HTG21:dGGG(TTAGGG)3in Na+solution
Circular dichroism,CD,is a useful technique to gain in-
formation about G-quadruplex DNA.It is also used to moni-
tor the thermal melting and the kinetics of the formation of G-
quadruplex[11].The temperature,at which the G-quadruplex
folded structure decomposed into the DNA unfold strand is
caled the melting temperature(Tm)that can be used to judge
the stability of G-quadruplex structure.If ligands bind to and
strengthen G-quadruplex structure,the Tmvalue of G-quadru-
plex wil be enhanced.By analyzing the melting curves shifts
at the sensitive wavelength in the CD spectrum,G-quadruplex
Tmcan be calculated and used to estimate the stability of com-
plex of ligand binding to G-quadruplex.
HTG21is reported to form different topological struc-
tures in different monovalent cation buffers.In Na+solution,
a basket-type structure is formed[12],whereas a mixture of
hybrid-1and hybrid-2type structures are formed in K+solu-
tion[13].Due to its simplicity,a basket-bal structure was
firstly chosen by us to observe if liliflorin A could stabilize
HTG21by CD spectrum.Berberine and Quercetin[14]were
used as positive controls.The change of the absorption at 295
nm in the CD spectrum,a typical signal corresponding to
HTG21in Na+ was recorded.The concentration of al the
compounds was changed gradualy from 0.0to 200.0μmol·
L-1 respectively.The data showed that the Tm value of
HTG21was enhanced in accordance to the incensement of Lil-
iflorin A concentration.The highest Tm was observed at
72.53℃under the concentration of 75.0μmol·L
-1 liliflorin
A.Compared with the Tmvalue of HTG21only in Na+solu-
tion,theΔTm was 1.94℃.In addition,liliflorin A showed
comparative ability on enhancing HTG21 Tm,compared to
berberine and quercetin at the same concentration(Table 1).
Table 1 The melting temperatures of treated HTG21 (5.0
μmol·L-1 strand concentration)after reacting with
compounds in a series of concentrations in 10.0
mmol·L-1 Tris-HCl buffer and 100mmol·L-1
NaCl at 25.0℃
concentrations
/(μmol·L-1)
Tmvalue of HTG21/℃a
Liliflorin A  Berberine  Quercetin
0  70.59  70.59  70.59
25.0  69.80  71.07  70.36
50.0  70.10  71.86  71.05
75.0  72.53  72.47  72.17
100.0  72.37  72.52  72.79
200.0  72.53  71.70  73.90
a:Al results are expressed as mean±SE for al groups(n=3)
  Due to the higher potassium concentration within the
cel,G-quadruplex structures in the presence of K+is more
relevant biologicaly than those topological structures in
Na+[15].Thus,K+solution was used in al the later experi-
ments.
2.2 Liliflorin A selectively stabilize human telomeric G-quad-
ruplex in FRET-melting
Because of its sensitivity and flexibility,fluorescence res-
onance energy transfer(FRET)is widely used to investigate
conformational changes of G-quadruplexes,and also becomes
very popular to study the interaction between ligands and G-
quadruplex[16].The melting curve could be described through
the normalized fluorescent quenching vs temperature plotting
though FRET-melting experiment,due to a large difference
between the fluorescence properties of the folded and unfolded
898 光谱学与光谱分析                    第36卷
doubly labeled oligonucleotides.By the analysis of the fluctu-
ation of the melting curve under the heating process,the Tm
can be given to evaluate the stability of complex of ligand
binding to G-quadruplex.In the experiment,HTG21is la-
beled with a FAM (fluorescent donor)on the 5’end and a
TAMRA(fluorescent acceptor)on the 3’end.This doubly
labeled oligomer was caled F21T.
2.2.1 Concentration-dependent experiment of interaction
between Liliflorin A and F21T
The melting temperature of F21Tin Tris-HCl buffer
containing of 60.0mmol·L-1 K+ was deeply studied under a
series of Liliflorin A concentration.Under the concentration
ranging from 1.0to 4.0μmol·L
-1,the melting curve of
F21Tindicated a high temperature shift gradualy [Fig.1
(a)],and the calculatedΔTmwas 0.26,1.07,1.61and 3.22
℃respectively.The enhancement of Tmstopped as Liliflorin
A concentration increased to 5.0and 6.0μmol·L
-1[Fig.1
(b)].The data showed that Liliflorin A interacted with
F21T,and stabilized the G-quadruplex in a concentration-de-
pendent manner.The highest Tm69.93℃ appeared at 4.0
μmol·L
-1.
Fig.1 FRET experiment was carried in 10.0mmol·L-1 Tris-
HCl buffer and 60.0mmol·L-1 KCl
(a):Melting curves of F21T(0.2μmol·L-1)in the presence of lili-
florin A in various concentrations.Curves with normalized FAM fluo-
rescence to a 0-1range;(b):ΔTmof F21Tin the presence of liliflorin
A in 1.0,2.0,3.0,4.0,5.0and 6.0μmol·L-1 respectively
2.2.2 Competitive FRET-melting experiment
To further prove the binding ability of liliflorin A to
F21T,a competitive FRET-melting experiment was studied,
in which the excess of unlabeled 26-bp duplex-DNA (ds26)
was added to the mixture system of 0.2μmol·L
-1 F21Tand
4.0μmol·L
-1 liliflorin A.As a result,little change of the
ΔTmcould be recorded(Fig.2),even when the concentration
of ds26reached 10.0μmol·L
-1,indicating that the duplex-
DNA ds26had no influence on the interaction between F21T
and liliflorin A.
Fig.2 Melting curves of the mixture of 0.2μmol·L-1 F21T
and 4.0μmol·L-1 liliflorin A in 3.0and 10.0μmol
·L-1 ds26respectively in 10.0mmol·L-1 Tris-HCl
buffer and 60.0mmol·L-1 KCl
2.2.3 Interaction between liliflorin A and F10Tby FRET-
melting experiment
F10T,was another folded structure of nucleic acids
which differed from G-quadruplex in having the hairpin loop
structure.In FRET-melting experiment,although liliflorin A
with concentration at 1.0,2.0,3.0,4.0,5.0and 6.0
μmol·L
-1 was added into the mixture of F10Trespectively,
ΔTmof F10Tremained unchanged,indicating that no interac-
tion between liliflorin A and the hairpin loop F10T [Fig.3
(a)].
2.2.4 Interaction of liliflorin A between F-myc-T and F-kit1
G-quadruplex by FRET-melting experiment
The other two G-quadruplexes found in the promoter re-
gions of myc and kit genes were also studied by FRET-melt-
ing experiment[17].F-myc-T and F-kit1,corresponding to the
doubly labeled sequences were used respectively.ΔTmof both
of the G-quadruplex were almost 0in al the experiments,
showing that the thermal stabilization of the G-quadruplex
formed by c-kit sequence and c-myc sequence were not influ-
enced,due to little interaction between liliflorin A and G-
quadruplex[Fig.3(b)and(c)].
2.3 Interactions between liliflorin A and HTG21,c-myc 2345
and c-kit G-quadruplex in the NMR experiments
Nuclear magnetic resonance spectroscopy(NMR)is an
essential tool in the study of G-quadruplex nucleic acids.Imi-
no protons atδ10~12ppm in 1 H-NMR spectrum corre-
sponding to guanine imino protons in G-tetrad formation[18]
998第3期                    光谱学与光谱分析
were characteristic signals for G-quadrplex.Changes in the
chemical shift values of the relevant imino protons could be
observed upon interaction between ligand and G-quadruplex.
Depending on the types of the changes,the binding mode and
the strength of the binding between the ligand and G-quadru-
plex can be proposed[5,19].
Fig.3 Melting curves of 0.2μmol·L-1(a)F10T,(b)F-
myc-T,(c)F-kit1in the presence of liliflorin A at
1.0,2.0,3.0,4.0,5.0and 6.0μmol·L-1 respec-
tively in 10.0mmol·L-1 Tris-HCl buffer and 60.0
mmol·L-1 KCl
  To verify the selective interaction between liliflorin A and
HTG21observed in FRET,1 H-NMR experiments were per-
formed.There were more than 12guanine imino protons sig-
nals atδ10~12ppm in the 1 H-NMR of HTG21G-quadru-
plex,indicating a mixture of conformations in K+ solu-
tion[13].After the addition of liliflorin A into HTG21solu-
tion,the 1 H-NMR spectra of the mixture was recorded every
one hour.It can be observed that five peaks became broad and
shifted upfield[Fig.4(a)and Fig.5]gradualy from 1to 3
hours,whereas,no more changes appeared after 3hours,
showing that liliflorin A bound to HTG21in 3hours.Moreo-
ver,there were not any changes in 1 H-NMR spectra of the
mixture of liliflorin A and c-myc2345or c-kit G-quadruplex
[Fig.4(b)and(c)],suggesting no interaction between lili-
florin A and c-myc 2345or c-kit G-quadruplex.
Fig.4 1 H-NMR spectra of 1.0mmol·L-1(a)HTG21,(b)
c-myc 2345,(c)c-kit G-quadruplex after reacting with
1mmol·L-1 liliflorin A in a:0h,b:1h,c:2h,d:
3h,and e:4hin 80% phosphate buffer (20.0
mmol·L-1 KH2PO4/K2HPO4,70.0 mmol· L-1
KCl,90%H2O/10% D2O,pH 7.4)and 20% DMSO
at 298K
2.4 Molecular Docking
There has been an increasing interest in using docking
method to carry out efficient and robust docking calculations
of promising drug candidates[20].Docking Server is a website
that handles al aspects of molecular docking from ligand and
bio-macromolecules set-up,provides ful control on the set-
009 光谱学与光谱分析                    第36卷
ting of specific parameters of ligand and bio-macromolecules
set up and docking calculations.Here,human telomere se-
quence dTAGGG(TTAGGG)3 Tel23was chosen as the G-
quadruplex model[21](2JSM in PDB).The two more bases
than Tel21reinforce the G-quadruplex of Tel23,thus its
structure model of HTG23can be found in PDB.
Fig.5 The chemical shifts’changes of the five guanine imino
protons in HTG21after reacting with liliflorin A for 3
hours
  According to the results from Docking,liliflorin A binds
to HTG23in 1∶1binding stoichiometry(Fig.6).The inhibi-
Fig.6 Hypothetical molecular models showing the interactions
of liliflorin A with human telemoric G-quadruplex
Tel23(PDB ID:2JSM).The loop of G-quadruplex is
shown in cartoon,and G-tetrad is shown in sticks,
while liliflorin A was represented with the red sticks
tion constant(Ki)is 387.40μmol·L
-1 and the free energy
of binding is-4.65kcal·mol-1(Table 2).Moreover,the
docking results indicated that liliflorin A binds to HTG23at
G9,G10,G16and G17(Fig.6).The calculation results con-
firmed the interaction between liliflorin A and HTG21ob-
served by spectroscopic experiments.
Table 2 Binding energies obtained from docking of liliflorin A to HTG23in the rank of five calculating
Rank
Est.Free Energy
of Binding/
(kcal·mol-1)
Est.Inhibition
Constant,Ki/
(μmol·L-1)
vdW+Hbond+
desolv Energy
/(kcal·mol-1)
Electrostatic
Energy
/(kcal·mol-1)
Total Intermol.
Energy
/(kcal·mol-1)
1 -4.65  387.40 -5.65 -0.23 -5.88
2 -4.41  582.00 -5.44 -0.10 -5.55
3 -4.34  657.38 -4.95 -0.45 -5.39
4 -4.20  834.94 -4.92 -0.42 -5.34
5 -4.40  983.68 -5.24 -0.25 -5.50
3 Conclusions
  Here,an efficient screening of natural products which
can interact with G-quadruplex by spectroscopic methods was
reported.The results of CD,FRET and NMR spectra,as
wel as the results of Molecular Docking were summarized,
and the folowing conclusions can be drawn:
(1)In CD experiments,compared with berberine and
quecertin,the melting temperature of HTG21in sodium salt
buffers was enhanced,indicating liliflorin A interacted with
HTG21and stabilized the G-quadruplex.
(2)In FRET experiments,HTG21 Tmpresented varia-
tion with the same trend of liliflorin A concentration,the
highestΔTm was 3.2℃at 4.0μmol·L
-1.In the competi-
tive circumstance,double strings DNA ds26had no influence
on theΔTmof HTG21.Furthermore,the Tmof F10Tand G-
quadruplex formed by c-myc and c-kit sequence presented lit-
tle fluctuation regardless of liliflorin A’s existence,indicating
the selectivity of liliflorin A toward HTG21.
(3)In NMR experiments,the spectra of HTG21showed
vivid alteration after reacting with liliflorin A in 3hours.No
changes were observed in those spectra of c-myc 2345and c-
kit sequence in 3hours.This phenomenon verified the better
selectivity of liliflorin A toward HTG21.
(4)In Molecular Docking,the results suggested liliflorin
A binds to HTG23at G9,G10,G16and G17,which were lo-
cated on wide groove at the first and second G-tetrad planes.
Colectively,liliflorin A,isolated from M.liliflora by
us,was reported here as the first lignan derivative,which
presented a new type of ligand of G-quadruplex,and may gen-
erate a new candidate for antitumor drug design targeting on
human telomeric G-quadruplex.
109第3期                    光谱学与光谱分析
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紫玉兰素A与人端粒G-四链体相互作用的光谱学研究,
第一个木脂素类衍生物与G-四链体相互作用
刘婷婷1,周 爽1,贾千澜1,王文蜀1,2*,闫晓倩1,张文浩3,王帅旗1,焦玉国1
1.中央民族大学生命与环境科学学院,北京 100081         
2.中央民族大学,北京市食品环境与健康工程研究中心,北京 100081
3.清华大学,生物医学测试中心,北京 100084
摘 要 人端粒G-四链体结构是指端粒末端富含鸟嘌呤(G)的DNA序列在一价阳离子(如K+和Na+)诱导
下通过G碱基间 Hoogsteen氢键连接形成的DNA二级结构。能够稳定端粒G-四链体的配体通常为端粒酶
抑制剂,其可能成为抗肿瘤药物。应用CD,FRET,NMR光谱方法第一次较全面地研究了一种木脂素衍生
物,紫玉兰素A(liliflorin A)与人端粒序列dGGG(TTAGGG)3G-四链体HTG21的相互作用,采用分子对接
技术进一步研究紫玉兰素A与人端粒序列dTAGGG(TTAGGG)3G-四链体 HTG23的结合位点。CD实验数
据表明紫玉兰素A提高 HTG21解链温度,FRET实验测得4.0μmol·L
-1紫玉兰素A可以将 HTG21稳定
温度提高3.2℃。NMR实验结果表明,加入紫玉兰素A三小时后 HTG21核磁谱图出现明显变化。分子对
接结果表明紫玉兰素A结合到 HTG23较宽沟槽上,结合位点为G9,G10,G16和G17。紫玉兰素A是第一
个能够选择性稳定人端粒G-四链体 HTG21的木脂素类衍生物配体。实验结果为以人端粒G-四链体为靶点
的抗肿瘤药物设计提供了新型候选化合物。
关键词 紫玉兰素A;G-四链体;人端粒;光谱分析;相互作用
  *通讯联系人 (收稿日期:2015-05-08,修订日期:2015-11-02)  
209 光谱学与光谱分析                    第36卷