Post-transcriptional processing

Goldman, D. S., Kiessling, A. A., and Cooper, G. M. (1988). Post-transcriptional processing suggests that c-mos functions as a maternal message in mouse eggs. Oncogene 3 159-162. 

Figure 4.27 The post-transcriptional processing of yeast tRNATyr. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.)...

Heterogeneous nuclear RNA (huRNA or pre-mRNA), which is found only in the nucleus of eukaryotic cells. It represents precursors of mRNA, formed during its post-transcriptional processing. 

In prokaryotes, RNA transcribed from protein-coding genes (messenger RNA, mRNA), requires little or no modification prior to translation. In fact, many mRNA molecules begin to be translated even before RNA synthesis has finished. However, ribosomal RNA (rRNA) and transfer RNA (tRNA) are synthesized as precursor molecules that do require post-transcriptional processing (see Topics G9 and G10, respectively). 

Further details of the nature and regulation of transcription in prokaryotes and eukaryotes and the post-transcriptional processing of mRNA transcripts are given in Chapter 9. 

FIGURE 3.31 The post-transcriptional processing of yeast tRNA . ... 

Observed increases in the endogenous activity of an enzyme may result from transcriptional activation of the corresponding gene, post-transcriptional processing of existing precursors of mRNA, or post-translational activation of inactive or less active enzymes. Increases in ACC synthase activity in response to auxin [32] and wounding... 

VorsL O., van Dam, F., Weisbeek, P, and Smeekens, S. (1993). Light-regulated expression of the Arabidopsis thaliana ferredoxin a gene involves both transcriptional and post-transcriptional processes. Plant J. 3, 793-803. 

Finally, some data (Holmquist, 1972) have shown that, on the phenotypic level of dose compensation, post-transcriptional processes are also important. 

Transcription produces RNA molecules. In prokaryotes, rRNAs and tRNAs are synthesized as longer precursors which require post-transcriptional processing including methylation and cleavage by specific endonucleases before they are functional molecules. Polycistronic mRNAs (Section 7.4) do not require further enzymic modification. 

In eukaryotes, three RNA polymerases have been identified. RNA polymerase I, located in the nucleolus (Section 9.4), synthesizes 5.8S, 18S, and 28S rRNA. RNA polymerase II, found in the nucleoplasm, participates in mRNA synthesis. RNA polymerase III, also identified within the nucleoplasm, functions in tRNA and 5S rRNA synthesis. Post-transcriptional processing similar to that of prokaryotic transcripts produces rRNAs and tRNAs. 

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