Substantially enhanced cloning efficiency of SAGE (Serial Analysis of GeneExpression) by adding a heating step to the original protocol

The efficiency of the original SAGE (Serial Analysis of Gene Expression) pr otocol was limited by a small average size of cloned concatemers. We descri be a modification of the technique that overcomes this problem. Ligation of ditags yields concatemers of various sizes. Small concatemers may aggregat e and migrate with large ones during gel electrophoresis. A heating step in troduced before gel electrophoresis breaks such contaminating aggregates. T his modification yields cloned concatemers with an average size of 67 tags as compared to 22 tags by the original protocol. It enhances the length of cloned concatemers substantially and reduces the costs of SAGE.