ABSTRACT
This chapter focuses on the enzymes from higher eukaryotes, particularly those of the animal kingdom. The structural genes for eukaryote proteins are large, complex DNA molecules, which, in many cases, contain a number of intervening sequences not found in the mature messenger ribonucleic acid. Regulation of the production of many eukaryote proteins occurs at the level of transcription. Cloned ribosomal DNA is accurately transcribed by polymerase I when microinjected into frog oocytes. Chromatographic resolution of three types of nuclear RNA polymerases was first reported in 1969. Physiological stimuli have been reported to alter the activity of solubilized RNA polymerase III. Accurate transcription of specific genes using highly purified RNA polymerase, deproteinized DNA, and purified regulatory factors is fast approaching reality. The advent of the cell-free system has resulted in elucidation of some of the protein factors involved in regulation of transcription by these polymerases.
