Posttranscriptional gene silencing in Neurospora by a RecQ DNA helicase

The phenomenon of posttranscriptional gene silencing (PTGS), which occurs w hen a transgene is introduced into a cell, is poorly understood. Here, the qde-3 gene, which is required for the activation and maintenance of gene si lencing in the fungus Neurospora crassa, was isolated. Sequence analysis re vealed that the qde-3 gene belongs to the RecQ DNA helicase family. The QDE 3 protein may function in the DNA-DNA interaction between introduced transg enes or with an endogenous gene required for gene-silencing activation. In animals, genes that are homologous to RecQ protein, such as the human genes for Bloom's syndrome and Werner's syndrome, may also function in PTGS.