Antimetabolites of Transcription and Translation

The biologist often needs to know whether the genetic material participates in a particular developmental process or not. Such participation can only occur via transcription and translation. It is therefore necessary to know whether the process under investigation involves transcription and translation or not. For this purpose substances that cause inhibition at a known step of transcription or translation are useful tools. For if the process under investigation is blocked after administration of specific inhibitors of this kind, then the involvement of transcription and translation is clearly implied. 

Substances which block intermediary metabolism are called general antimetabolites. Two kinds of such antimetabolites are of interest here, structural analogs and antibiotics. 

Most of these are synthetic substances which are very similar to the natural metabolites. For this reason, they can be used as substitutes for the natural metabolites in metabolism. In the present context the structural analogs of the nucleic acid bases and of amino acids are important (Fig. 13). Both groups can cause inhibition by two mechanisms. 

Irrespective of the mechanism, both kinds of inhibition interfere with transcription or translation. However, one point must always be borne in mind when antimetabolites are being used both structural analogs and antibiotics, which we shall discuss presently, can produce side effects 

The last-mentioned requirement is met ideally in the case where only the transcription and translation steps of the process under investigation are inhibited. If possible, other processes which also depend on transcription and translation should not be impaired. In other words, one should try to interfere with the process under investigation as selectively as possible. It goes without saying that the attainment of such selective inhibition is not easy and certainly cannot always be achieved. A little later we will discuss several examples in some detail. 

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