50+ years of eukaryotic transcription: an expanding universe of factors and mechanisms.

The landmark 1969 discovery of nuclear RNA polymerases I, II and III in diverse eukaryotes represented a major turning point in the field that, with subsequent elucidation of the distinct structures and functions of these enzymes, catalyzed an avalanche of further studies. In this Review, written from a personal and historical perspective, I highlight foundational biochemical studies that led to the discovery of an expanding universe of the components of the transcriptional and regulatory machineries, and a parallel complexity in gene-specific mechanisms that continue to be explored to the present day.