Supplementary material
Supplementary methods
Vector construction
To construct the miR-1228 expression vector (pcDNA3/pri-miR-1228), we first amplified a
DNA fragment carrying pri-miR-1228 from genomic DNA using the pri-miR-1228-sense (S)
and -antisense (AS) primers shown in Supplementary Table 1. The amplified fragment was
then cloned into the pcDNA3 vector using the EcoRI and BamHI sites.
To construct the enhanced green fluorescent protein (EGFP) reporter plasmid, the
wild-type p53 mRNA 3’UTR was amplified by PCR using the TP53-1228-3’UTR-S and -AS
primers and was inserted into downstream of the EGFP gene between the EcoRI and BamHI
(TaKaRa, Madison, WI) sites in the pcDNA3/EGFP plasmid. Additionally, a 3’UTR fragment
containing the mutated miR-1228 binding site was amplified using PCR site-directed
mutagenesis. The two additional primers were TP53-1228-3’UTR-MS and -MA. The PCR
product was inserted into the pcDNA3/EGFP plasmid using the same sites to form the
reporter
vector
pcDNA3/EGFP-p53-3’UTR
mut.
The
2-O’-methyl-
and
3’-amino-C6-modified anti-miRNA oligomers (ASO-miR-1228 and ASO-NC) were obtained
from Shanghai GIMA Company.
The 866 bp and 1546 bp miR-1228 promoter regions spanning from -1328 bp upstream
to -462 or 218 of the LRP1 5’UTR were amplified from the genomic DNA of QGY-7703 cells
using
the
primers
LRP1/miR-1228p-S,
LRP1/miR-1228-p1546-AS,
and
LRP1/miR-1228-p866-AS, as shown in Supplementary Table 1. The fragments were then
inserted into the KpnI and EcoRI restriction sites of the pGL3 basic luciferase reporter vector
(Promega,
Madison,
WI).
The
constructs
were
designated
as
pGL3-Basic-luc+
LRP1/miR-1228-p866 or LRP1/miR-1228-p1546. The primers used to construct the mutant
promoters (LRP1/miR-1228-mut-S and LRP1/miR-1228-mut-AS) are also shown in
Supplementary Table 1. The mutated fragment was amplified using a PCR site-directed
mutagenesis assay, and the fragment was then inserted into the pGL3 basic luciferase reporter
vector using the same sites to form the LRP1/miR-1228-mut. reporter vector (Figutr 5D,
where the red letters indicate the sites of mutation). The details of the primer sequences can
be found in Supplementary Table 1.
RNA extraction and quantitative reverse-transcription PCR (qRT-PCR)
Total RNA was extracted using the Trizol reagent (Invitrogen) and was reverse transcribed to
generate cDNA using oligo-dT primers (for mRNA) or stem-loop reverse transcriptase (RT)
primers (for miRNA). Quantitative RT-PCR was performed in a LightCycler (Bio-Rad,
Hercules, CA) using the SYBR Premix Ex Taq. U6 snRNA and the β-actin housekeeping gene
were used as endogenous controls for miRNA and mRNA, respectively. For mature miRNAs,
the reactions were incubated at 94°C for 10 min, followed by 40 cycles of 94°C for 30 s, 60°C
for 30 s, and 72°C for 30 s. For mRNA, the following conditions were used: 94°C for 10 min,
followed by 40 cycles of 94°C for 30 s, 56°C for 30 s, and 72°C for 30 s. The details of the
primer sequences can be found in Supplementary Table 1.
Western blot
To harvest the total protein, the cells were lysed with RIPA lysis buffer. Cell lysates was
separated on 10% SDS denaturing PAGE gels and were transferred to the nitrocellulose
membranes (HybondECL). The membranes were then blocked in PBS/Tween-20 containing
5% nonfat milk. The membranes were incubated overnight at 4°C with polyclonal rabbit
anti-p53 and rabbit anti-GAPDH antibodies (Saierbio, Tianjin, China). The membranes were
then washed and incubated with anti-rabbit IgG-HRP for 2 hrs. The protein expression level
was assessed by enhanced chemiluminescence and exposure to chemiluminescent film
(Fujifilm, Tokyo, Japan). Lab Works image acquisition and analysis software (UVP) was used
to quantify the band intensities.
Cell colony formation
Hepatocellular carcinoma cells were seeded in 96-well plates. Twenty-four hours later, the
cells were transfected with pcDNA3-p53 and shR-p53 or the corresponding controls. For
colony formation, the cells were counted and seeded in 12-well plates at a density of 300
(QGY-7703) or 800 (HepG2) cells per well after transfection. Culture medium was replaced
every 3 days. On the 10th-14th day after seeding, the cells were stained using crystal violet,
and each colony with a minimum of 50 cells was counted.
Migration and invasion assays
For the transwell migration assay, QGY-7703 or HepG2 cells were trypsinized 24 hours after
transfection. Then, 5×104 QGY-7703 cells or 12×104 HepG2 cells in 0.2 ml RPMI-1640 or
MEM- without fetal bovine serum (FBS) were placed in the top chamber of each insert
(Millicell, Millipore) without Matrigel. For the invasion assay, before placing the cells, each
insert was coated with 40 l of Matrigel (Clontech, Mountain View, CA), which was diluted
to 4 g/l with RPMI-1640 medium for the QGY-7703 cells or 1 g/l with MEM-α medium
for the HepG2 cells. The lower chamber was filled with 700 l of RPMI-1640 medium for the
QGY-7703 cells or MEM- medium for the HepG2 cells; both media were supplemented
with 20% FBS to act as a nutritional attractant. After several hours of incubation (10 hrs for
QGY-7703 and 22 hrs for HepG2 in the migration assays; 24 hrs for QGY-7703 and 48 hrs for
HepG2 in the invasion assays), the migrated cells that were attached to the lower surface were
fixed with 20% methanol, followed by staining with crystal violet for 30 min. Once dry, the
membranes were excised from the insert and embedded under cover slips to quantify the
migrated cells; five random fields of view were counted for each membrane. All assays were
repeated at least in triplicate, and the results are expressed as the mean ± SD.
Cell cycle analysis by flow cytometry
Transfected QGY-7703 cells were plated in duplicate in 6-well plates and incubated for 24 h
in complete culture medium. One group of cells was deprived of serum for 24 h prior to
harvest, whereas another group of cells was returned to complete medium for another 24 h
before harvest. The cells were collected by centrifugation, fixed in 95% (v/v) ethanol, and
stored at -20°C overnight. After washing with phosphate-buffered saline (PBS), the cells were
resuspended in propidium iodide (PI) staining buffer (PBS, 0.1% Triton X-100, 60 g/ml PI,
0.1 mg/ml DNase-free RNase, and 0.1% trisodium citrate) for 30 min on ice. The DNA
content was analyzed using a FACSCalibur flow cytometer (BD Biosciences) and Cell Quest
software (BD Biosciences).
Supplementary figures and figure legends
Supplementary Figure 1. miR-1228 promotes the growth and migration/invasion of HepG2
cells. (A) Colony formation assays of HepG2 cells that were transiently transfected with
pcDNA3/pri-miR-1228, ASO-miR-1228, or a control vector. (B) Transwell migration assay of
HepG2 cells. (C) Transwell invasion assay of HepG2 cells. Representative images are shown.
Cells in five random fields of view were counted at 100× magnification.
Supplementary Figure 2. p53 inhibits the proliferation of QGY-7703 and HepG2 cells. (A
and B) p53 mRNA and protein levels were examined by qRT-PCR and western blot analysis,
respectively; 48 hours later, the cells were transfected with the shR-p53, pcDNA3-p53, or a
control vector. β-actin and GAPDH were used as the internal controls for quantitative
normalization, and the control groups transfected with the pcDNA3 empty vector or shR-NC
were set to 1. (C and D) QGY-7703 cells were transfected with either pcDNA3-p53 or
shR-p53 and were seeded to reveal the cell growth ability. The results for the HepG2 cells
were similar to the colony formation results in the QGY-7703 cells.
Supplementary Figure 3. p53 inhibits the metastasis of QGY-7703 and HepG2 cells. (A and
B) The transwell migration and (C and D) invasion assays were performed to evaluate the
metastatic capacity of the QGY-7703 and HepG2 cells after transfection with pcDNA3-p53,
shR-p53, or their control plasmids.
Supplementary Figure 4. Restoration of p53 abrogates the effects induced by miR-1228 in
HepG2 cells. (A) The colony formation assay revealed that with miR-1228 present, the
average colony formation rate in the HepG2 cells was decreased following expression of p53
without a 3’UTR. (B) Ectopic expression of p53 without a 3’UTR decreased the migration of
the HepG2 cells when miR-1228 was present. The average number of migrated cells was
determined from three independent experiments. (C) Similar results for the cell invasion
assay were obtained in the HepG2 cells.
Supplementary Table 1.
Sequence of the primers used in this study.
Primer
Sequence(5'-3')
pri-miR-1228-S
CATTCGGATCCCAAGAACAGACTCGCAC
pri-miR-1228-AS
GGGAGAATTCGGGGAGAGTTCAGGTAGATG
ASO-miR-1228
GGGGGGCGAGGCAGGTGTGA
ASO- NC
GTGGATATTGTTGCCATCA
TP53-1228-3'UTR-S
CATGGATCCCTTGTTCCCCACTGACAGCC
TP53-1228-3'UTR-AS
CTTGAATTCTCCCCATCCTCCTCCCCACAAC
TP53-1228-3'UTR-MS
CCTTGCTTGCAATACCTCTCCGTCAGAAGCACC
TP53-1228-3'UTR-MA
GGTGCTTCTGACGGAGAGGTATTGCAAGCAAGG
TP53-qPCR-S
TTGAGGTGCGTGTTTGTG
TP53-qPCR-A
AGTTTTTTATGGCGGGAG
β-actin-S
CGTGACATTAAGGAGAAGCTG
β-actin-AS
CTAGAAGCATTTGCGGTGGAC
miR-1228 RT
GTCGTATCCAGTGCAGGGTCCGAGGTATTCGCACT
GGATACGACGGGGGG
miR-1228 Forward
TCACACCTGCCTCG
U6 RT primer
GTCGTATCCAGTGCAGGGTCCGAGGTATTCGCACT
GGATACGACAAAATATGGAAC
U6 Forward primer
TGCGGGTGCTCGCTTCGGCAGC
Reverse primer
CCAGTGCAGGGTCCGAGGT
LRP1/miR-1228p-S
GGGGTACCGGAGGCAAGTCCTTCGTG
LRP1/miR-1228-p1546-AS
CGGAATTCTTCACTCCTCGCTGCTCT
LRP1/miR-1228-p866-AS
CGGAATTCTGAAGGTGCCTCCTCTGC
LRP1/miR-1228-mut-S
GCGGGCGTCGACAGACTCAGGTGTCCCCTCGGGA
CACTGTGTTTAC
LRP1/miR-1228-mut-AS
GTAAACACAGTGTCCCGAGGGGACACCTGAGTCT
GTCGACGCCCGC
Reference
Xiao J, Lin H, Luo X, Luo X, Wang Z (2011). miR-605 joins p53 network to form a
p53:miR-605:Mdm2 positive feedback loop in response to stress. The EMBO journal 30(24): 5021.