RNA interference libraries prove their worth in hunt for tumor suppressor genes.

RNA interference has been promoted as an ideal tool for functional genomics, but to date the success stories have principally been in model organisms. Two papers in this issue of Cell change all that: use of RNA interference libraries targeting large proportions of the human genome to uncover two novel tumor suppressor genes. REST is a transcriptional repressor that silences neuron-specific gene expression, and PITX1 is a homeodomain transcription factor that promotes the expression of a negative regulator of Ras.