A computer program is presented that selects a small set of short primer pairs for PCR to sample all the sequences in a user -specified list of mRNAs. Such primer pairs could be used to increase the probability of sampling mRNAs of particular interest in differential dis
INTRODUCTIONThe polymerase chain reaction (PCR) uses specific DNA primers to amplify specific sequences from a complex source of nucleic acids (13). If arbitrarily selected primers are used instead, then a reproducible fingerprint of products can be generated under the appropriate conditions (8,20,21). Arbitrary primers initiate PCR from sites on the template with varying efficiencies depending on the quality of the overall match and with particular regard to the match at the 3 ′ end of the primer. Relatively efficient priming events within a few thousand base pairs and facing each other on opposite strands, lead to PCR-amplifiable products. Products that are the most efficiently primed and most efficiently amplified compete most effectively in the subsequent PCR amplification and are visualized as a fingerprint after gel electrophoresis.This method was first applied to detect polymorphisms among related genomes because differences in primer-binding sites result in differences in the resulting PCR products (21,26). Later, the method was applied to studying differential expression of arbitrarily sampled RNAs (8,20). Differences in a cDNA PCR product derived from two isogenic RNA samples reflected differences in the abundance of the mRNA between the populations.One of the features of the method that could be changed is the arbitrary nature of the sampling. The first efforts to direct PCR fingerprints to particular sequences were applied to genomic DNAs. For example, the rate of detection of polymorphisms in higher eukaryote nuclear DNA could be increased by using primers that target the more polymorphic simple repeats or hyper-mutable methylation sites (25). Primers can also be directed towards sequences that are more frequent in some bacterial genomes (12,22,24,27).PCR with pairs of degenerate primers derived from back translation of conserved amino acid motifs have been widely used for finding new members of gene families (e.g., Reference 3). Similarly, PCR fingerprinting with primers derived from conserved motifs sometimes enriches for genes of interest (4,18,28). Another approach to selecting primers for targeted fingerprinting is to determine which oligonucleotide sequences are common in the list of sequences of interest and determine which pairs of primers will give a significant number of PCR products from these sequences. With the addition of arbitrary 5 ′ tails, these primers can then be used at relatively high stringency to sample sequences from the family of interest; although, other mRNAs could also be sampled by the same primers (9).We present a program to effectively select perfectly matched primer pairs for all or most of the sequences in a list of interest. Primers that match hyper -abundant RNAs are excluded.
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