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The post-transcriptional gene silencing mechanism in Neurospora crassa, called quelling, was shown to involve the products of three genes termed quelling-defective. A homologue to the qde-3 gene encoding a putative RecQ-type DNA helicase was isolated and was named RecQ-2. Characterisation of the RecQ-2 gene has revealed that it is not involved in quelling, but may co-operate with the qde-3 gene product in a pathway that repairs damage to DNA caused by the chemical mutagens methyl methanesulfonate and N-methyl- N'-nitro- N-nitrosoguanidine. These results indicate that the qde-3 RecQ helicase may have a dual role in N. crassa, either acting alone as an essential component of the quelling mechanism or together with the RecQ-2 RecQ helicase, as part of a process to repair DNA lesions during replication.