This volume represents the proceedings of the 24th Mos bach Colloquium on "Regulation of Transcription and Trans lation in Eukaryotes" which was held April 26-28, 1973, in Mosbach, Germany, under the auspices of the Gesellschaft fiir Biologische Chemie. To the three of us (H. KERSTEN, P. KARLSON and myself) who were commissioned with the invitation of speakers, it was a difficult decision as to whether we should attempt to cover with some twenty contributions as many aspects of this broad topic as possible, or to sacrifice the intellectually perhaps more pleasing but more specula tive concepts and to concentrate on a few aspects of gene expression in reasonable detail. We unanimously decided on the latter course, leaving such important and timely topics as for example, hormone action, cyclic AMP and reverse transcription to the proceedings of other symposia, and con centrating on the four questions which are most basic to an understanding of the mechanisms of transcription and trans lation and for which fragmentary but nonetheless reliable experimental results have become available within the last few years. These are the structure of chromatin, the syn thesis of messenger RNA, the structure of the active ribo some, and the role of initiation factors in protein synthesis.

During the last decade physical and chemical methods have improved rapidly - a fact which allowed the mode of action of antibiotics to be studied - and many biochemically-oriented scientists have devoted their research to the following questions: 1. What is the metabolic pathway that is inhibited selectively, and what are the target molecules within a sensitive cell? 2. What are the relationships between the chemical structure of an antibiotic and the physicochemical properties of the sensitive mole cule(s)? 3. Why and how far is the action selective? 4. Is it possible to correlate the interaction with the target mole cule(s) with the particular biological activities observed? This monograph deals with those antibiotics which interfere with the biosynthesis of nucleic acids. The idea was to provide an insight into how to investigate the preceding questions experimentally and to solve as yet unresolved problems rather than to give a review of the current state of knowledge. Although the biochemistry of nucleic acid synthesis is known in general, the precise molecular mechanisms by which deoxyribonucleic acid is replicated or transcribed has still to be clarified. For this reason it is not yet possible to describe the molecular mechanisms by which the inhibitors of nucleic acid and protein synthesis exhibit their effects. The fact that the inhibitors of nucleic acid and protein synthesis themselves served as useful tools to obtain an insight into the mechanisms of replication, transcription and translation was one of the most exciting discoveries in this field."