GeneRacer™ Kit with SuperScript™ III RT and TOPO TA Cloning™ Kit for Sequencing

You can store your cDNA at 2-6 degrees C for up to 24 hours. For long-term storage, store the cDNA at -15 to -25 degrees C and add EDTA to a final concentration of 1 mM to prevent degradation.

The GeneRacer method is designed to ensure that only full-length messages are ligated to the GeneRacer RNA Oligo and PCR amplified after cDNA synthesis. It is highly recommended that you clone your RACE products and analyze at least 10-12 colonies to ensure that you isolate the longest message. Many genes do not have only one set of transcription start sites but rather multiple transcription start sites spanning sometimes just a few or other times a hundred or even more bases. Cloning of the RACE products and analyzing multiple colonies ensues that you detect the diversity of the heterogeneous transcription start sites of your gene. It is also possible that you might obtain PCR products that may not represent the full-length message for your gene. PCR products that do not represent full-length message may be obtained because:

-RNA degradation after the CIP reaction creates new truncated substrates with a 5' phosphate for ligation to the GeneRacer RNA Oligo. Be sure to take precautions to ensure that the RNA is not degraded.
-CIP dephosphorylation was incomplete. Increase the amount of CIP in the reaction or decrease the amount of RNA.
-PCR yielded a PCR artifact and not true ligation product. Optimize your PCR using the suggestions described above.

RACE PCR artifacts or nonspecific PCR bands can result from one or more of the following:

-Nonspecific binding of GSPs to other cDNAs resulting in the amplification of unrelated products as well as desired products.
-Nonspecific binding of GeneRacer primers to cDNA resulting in PCR products with GeneRacer primer sequence on both ends of the PCR product.
-RNA degradation.
-Contamination of PCR tubes or reagents.
Note: Artifacts usually result from less than optimal PCR conditions and can be identified in negative control PCR.

Please see the following causes and suggestions:
Contamination by genomic DNA or an unexpected splice variant - Pretreat RNA with DNase I, amplification grade (Cat. No 18068015).
Design primers that anneal to sequences in exons on both sides of an intron or at the exon/exon boundary of the mRNA to differentiate between amplified cDNA and potential contaminating genomic DNA.
To test if products were derived from DNA, perform a minus RT control.
Nonspecific annealing of primers - Vary the PCR annealing conditions.
Use a hot-start PCR polymerase.
Optimize magnesium concentration for each template and primer combination.
Primers formed dimers - Design primers without complementary sequences at the 3' ends.

Please see the following causes and suggestions:

Procedural error in first-strand cDNA synthesis - Use high-quality RNA as a control to verify the efficiency of the first-strand reaction.
RNase contamination - Add control RNA to sample to determine if RNase is present in the first-strand reaction. Use an RNase inhibitor in the first-strand reaction.
Polysaccharide co-precipitation of RNA - Precipitate RNA with lithium chloride to remove polysaccharides, as described in Sambrook et al.
Target mRNA contains strong transcriptional pauses - Use random hexamers instead of oligo(dT) in the first-strand reaction, increase the temperature, and use PCR primers closer to the 3' terminus of the target cDNA.
Too little first-strand product was used in PCR - Use up to 10% of first-strand reaction per 50 mL PCR.
Gene-specific primer was used for first-strand synthesis - Try another set of GSP or switch to oligo(dT). Make sure the GSP is the antisense of the sequence.
Inhibitors of RT present - Remove inhibitors by ethanol precipitation of mRNA preparation before the first-strand reaction. Include a 70% (v/v) ethanol wash of the mRNA pellet. Note: inhibitors of RT include SDS, EDTA, guanidinium salts, formamide, sodium pyrophosphate, and spermidine.
RNA has been damaged or degraded - Ensure that high-quality, intact RNA is being used.
Annealing temperature is too high - Decrease temperature as necessary and/or use touchdown PCR.