The RNA Polymerase II Carboxy-Terminal Domain (CTD) Code

The smallest viable unit of life is the cell. From bacteria to mammals, all cells use the same nucleic acid-based universal code for the maintenance and inheritance of genetic information. All life on earth probably started with a common ancestral cell approximately 4 billion years ago. Today, a huge diversity of organisms live on Earth, many of them still at the evolutionary stage of unicellular organisms, while others are life forms of high complexity with large cell numbers. The development of this diversity was driven by evolution, a process assuring survival and adaption of life to new environmental challenges. While the first evolutionary processes were probably very simple genetic changes, these processes gradually became more sophisticated with the development of higher eukaryotes. The remaining major part of the genome, including all coding genes, is transcribed by RNAPII. It was first assumed that RNAPII transcription might be limited to genomic loci that give rise to messenger RNA (mRNA) or other stable transcripts.