Method enabling fast partial sequencing of cDNA clones

Pyrosequencing is a nonelectrophoretic single-tube DNA sequencing method that takes advantage of cooperativity between four enzymes to monitor DNA synthesis. To investigate the feasibility of the recently developed technique for tag sequencing, 64 colonies of a selected cDNA library from human were sequenced by both pyrosequencing and Sanger DNA sequencing. To determine the needed length for finding a unique DNA sequence, 100 sequence tags from human were retrieved from the database and different lengths from each sequence were randomly analyzed. An homology search based on 20 and 30 nucleotides produced 97 and 98% unique hits, respectively. An homology search based on 100 nucleotides could identify all searched genes. Pyrosequencing was employed to produce sequence data for 30 nucleotides. A similar search using BLAST revealed 16 different genes. Forty-six percent of the sequences shared homology with one gene at different positions. Two of the 64 clones had unique sequences. The search results from pyrosequencing were in 100% agreement with conventional DNA sequencing methods. The possibility of using a fully automated pyrosequencer machine for future high-throughput tag sequencing is discussed.