RT-q PCR REAGENTS
2
PrimeScript RT synthesizes cDNA at 42°C with
high specificity and yield
Extension products obtained with PrimeScript RT were
compared with products generated by six other commer-
cially available RTs. An RNA ladder (containing 1, 2, 4.4, 6.4,
8.4, 10, and 12 kb fragments) was used as the template for
first strand cDNA synthesis. Each reaction was assembled
and performed according to the manufacturer’s recommen-
dations. Equivalent amounts of cDNA were loaded onto
an alkaline denaturing gel. After electrophoresis, the gel
was stained with SYBR
®
Green II, and the products were
detected by fluorescence imaging (Figure 2).
The yield of full-length cDNAs was far higher for Prime-
Script RT than any of the other enzymes. In addition,
although the reaction temperature for PrimeScript RT was
lower (42°C), the resulting cDNA had significantly less back-
ground arising from non-specific priming events.
PrimeScript RT is highly accurate
Several different RTs were used to synthesize first-strand
cDNA from human placenta total RNA (Clontech
®
Cat.
#636527) using oligo-dT primers. Reactions were per-
formed following each manufacturer’s recommended
protocol. After cDNA synthesis, PCR amplification of the
TF gene was performed with high-fidelity PrimeSTAR
®
HS
DNA Polymerase (Clontech Cat. # R010A). The 500 bp ampli-
fied fragments were then cloned into vectors, and multiple
clones were chosen for DNA sequence analysis. The error
rate was defined as the number of errors per total number
of bases sequenced (~200,000 bases). A PCR fragment
directly amplified from human genomic DNA was used as
a control. PrimeScript RT resulted in only 7 errors out of
200,000 bases (an error rate of just 0.0035%), the highest
accuracy of all RTs analyzed (Figure 3).
PrimeScript RT facilitates easy workflow
During synthesis of long RNA products by reverse
transcription, conventional enzymes require that the RNA
template be denatured first, followed by addition of RT. This
is intended to avoid the suppression of cDNA synthesis
that can occur when RT anneals to double-stranded RNA
secondary structures. In contrast, PrimeScript RT does not
require template denaturation, allowing greater flexibility in
workflow.
The yield of an 8 kb dystrophin cDNA product produced
by PrimeScript RT and Company L’s RT was examined by
RT-PCR. Three different protocols were compared as shown
in Figure 4: 1) denaturation of RNA template followed
by addition of RT on ice; 2) pre-incubation at the RT
reaction temperature (42°C for PrimeScript RT or 50°C for
Company L’s RT) followed by addition of RT at the reaction
temperature, but without prior template denaturation; or
3) addition of RT to template on ice, then shifting to the
reaction temperature. While PrimeScript RT produced cDNA
with all protocols, Company L’s RT generally showed poor
yield and absence of product when RT was added without
prior template denaturation (protocol 3).
PCR
Protocol
Oligo dt primer
dNTP
Total RNA
(0.1; 1; 10 ng)
RT (15-30 min)
RT inactivation
Target:
Dystophin 8 kb
Denature RNA
and add
RT on ice
Pre-incubate at
42°C or 50°C
then add RT
Add
RT on ice
65°C
42°C
or
50°C
0°C
Add RT
PrimeScript RT
(RT at 42°C)
Company L RT III
(RT at 50°C)
321
3
3
2
2
1 321
1
Figure 4: cDNA synthesis suppression by addition of RT to
non-denatured RNA.
Figure 3: Accuracy of various RTs.
RT Bases
sequenced
Error
(bases)
Error rate (%)
PrimeScript RT 201,297 7 0.0035
Company L RT II 166,227 9 0.0054
Company L RT III 161,409 11 0.0068
Company A RT 132,962 13 0.0098
M-MLV (Takara) 144,504 15 0.0104
Control (PCR only)
156,188 1 0.0006
Figure 2: First strand cDNA synthesis with various RTs.
kb
12 -
10 -
8.4 -
6.4 -
4.4 -
2.0 -
1.0 -
1 2 3 4 5 6 7 8
Figure 2:
First strand cDNA synthesis with
various RTs
1: PrimeScript RT 200 U
2: PrimeScript RT 10 0 U
3: Company L RT III
4: Company P RT
5: Company A RT
6: Company T RT
7: Company R RT
8: Company Q RT