Results
Outline of the R-PCR method
The R-PCR method is essentially divided into three main sections (Fig. 1 and Supplementary Fig. 1) and includes specifically designed testers, drivers, a single primer, a thermostable restriction enzyme (ApeKI), a thermostable Taq DNA polymerase and dNTPs. A brief description of the R-PCR method is as follows: 1) Section 1, tester and driver preparation. The preparation of tester and driver starts from samples digestion with ApeKI and MseI. The tester is made by ligation with an adaptor containing a polyA tail and then oligo-dT column purification. The driver is made by ligation of different adaptors, PCR amplification, and digestion with MseI. 2) Section 2, R-PCR reactions. The tester and driver are mixed and subjected to R-PCR with a single primer in the presence of ApeKI, which results in linear amplification of the desired fragments without ApeKI digestion due to design of a mismatch in the adaptor. In contrast, common undesired fragments are extended from the 3′ end of the driver to create the ApeKI site, which is cut, removing those fragments from further amplification. 3) Section 3, recovery of the desired fragments and the products are cloned. Recovery of the desired fragments from linear amplification in the previous step is carried out using selective PCR primers, and the products are cloned by Invitrogen's TOPO TA cloning system. Detailed procedure refers to Figure 1 and Supplementary Figure 1.