Nucleotides posttranscriptional modification

These processes are summarized in Figure 28-1. We have examined several of these mechanisms in previous chapters. Posttranscriptional modification of mRNA, by processes such as alternative splicing patterns (see Fig. 26-19b) or RNA editing (see Box 27-1), can affect which proteins are produced from an mRNA transcript and in what amounts. A variety of nucleotide sequences in an mRNA can affect the rate of its degradation (p. 1020). Many factors affect the rate at which an mRNA is translated into a protein, as well as the posttranslational modification, targeting, and eventual degradation of that protein (Chapter 27). 

Figure 5-22. Synthesis of tRNA. D, T. y, and are unusual nucleotides produced by posttranscriptional modifications.

Posttranscription modification of tRNA The synthesis of tRNA involves modification of some uridine nucleotides to unusual nucleotides, such as pseudouridine, ribothymidine, and dihydrouridine. 

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