RNA interference in Cryptococcus neoformans.

RNA interference (RNAi) is an experimental technique used to suppress individual gene expression in eukaryotic cells in a sequence-dependent manner. The process relies on double-stranded RNA (dsRNA) to target complementary messenger RNA for degradation. Here, we describe two plasmid-based strategies we have developed for RNAi in Cryptococcus neoformans. The pFrame vector utilizes the ACT1 promoter to enable the constitutive synthesis of hairpin RNA (hpRNA), the stem of which constitutes the dsRNA trigger. The pIBB103 vector relies on convergent, inducible GAL7 promoters to independently drive the synthesis of the sense and antisense strands of the interfering sequence; these strands anneal to form the initiating dsRNA molecule. Both vectors are designed to co-silence a "sentinel" gene with an easily scored phenotype to help identify clones in which RNAi is most effective. We provide guidelines for selecting a suitable interfering sequence to trigger RNAi in C. neoformans and describe the steps for subcloning into either vector, transforming C. neoformans by electroporation, screening clones for RNAi-related phenotypes, and evaluating the efficacy and specificity of gene silencing by RNAi.