Schematic of Myc function in Drosophila. The majority of RNA Polymerase II transcribed direct Myc targets (defined as genes that are bound and activated by Myc) control ribosome biogenesis (RiBi genes) or code for ribosomal proteins. The area of each group is proportional to the number of genes it contains; intronic snoRNAs are counted as direct Myc targets if their host genes are direct Myc targets. Previously, Myc has been shown to activate RNA Polymerases I and III and hence the transcription of rRNAs and tRNAs. Thus, the major function of Drosophila Myc resides in the control of protein synthesis. snoRNA, small nucleolar RNA.