 Components of the RNAi pathway are used in many eukaryotes in the maintenance of the organization and structure of their genomes.Modification of histones and associated induction of heterochromatin formation serves to downregulate genes pre-transcriptionally; this process is referred to as RNA-induced transcriptional silencing (RITS), and is carried out by a complex of proteins called the RITS complex.In fission yeast this complex contains argonaute, a chromodomain protein Chp1, and a protein called Tas3 of unknown function.