Transcription by RNA polymerase III: more complex than we thought.

RNA polymerase (Pol) III is highly specialized for the production of short non-coding RNAs. Once considered to be under relatively simple controls, recent studies using chromatin immunoprecipitation followed by sequencing (ChIP-seq) have revealed unexpected levels of complexity for Pol III regulation, including substantial cell-type selectivity and intriguing overlap with Pol II transcription. Here I describe these novel insights and consider their implications and the questions that remain.