Cellular Sites of RNA Synthesis

Abstract

Publisher Summary The chapter discusses the more recent experimental work on the sites of RNA synthesis and the intracellular transport or redistribution of the RNA molecules. A primary question is whether all the cellular classes of RNA are synthesized under the immediate control of DNA templates or whether the cells contain mechanisms for self-replication of one or more cellular RNA types. A decisive answer is provided, by an abundance of new experimental work of a type representing, to a large degree, a cross between the biochemical and cytological approaches. A large body of evidence shows that the synthesis of all ribosomal ribonucleic acid (rRNA), molecular ribonucleic acid (mRNA), and small ribonucleic acid (sRNA) is immediately DNA-dependent and restricted to the cell nucleus. RNA synthesis occurs independently on both the chromosomes and in the nucleoli. Some evidence suggests that nucleoli may accumulate RNA from other parts of the nucleus, but there is no satisfactory evidence that nucleolar RNA passes to the chromosomes. There is no evidence that RNA of these classes can undergo self-replication, within the cells, and all cytoplasmic RNA must be derived from the nucleus.