The Functions of RNA

The cell nucleus is the repository of primary genetic information, as encoded in the DNA (cf., Gray, in Devlin, 1986, p. 872ff). This information must be transferred from the DNA to the protein-synthesizing machinery, which is located in the cytoplasm outside the nucleus. The macromolecules or intermediaries that transfer this information reflect the makeup of the DNA, and by virtue of their chemical composition are called ribonucleic acids, or RNAs, the transfer process itself being called transcription. 

It may be added that RNA comes in different molecular forms, for different purposes, and include what are called messenger RNA, or mRNA transfer RNA, or tRNA and ribosomal RNA, or rRNA. Although RNA is chemically very similar to DNA, it is relatively unstable, being rapidly degraded after synthesis and use. 

With both DNA and RNA synthesized or involved in reactions catalyzed by specific enzymes, there are in turn enzyme inhibitors for these enzyme catalysts. Examples are listed for both DNA and RNA in Appendix E and Appendix F, respectively, of Hoffman (1999). The listing is extensive, indicating that the biochemistry is quite involved. 

As for inhibitors, some of the more common compounds or substances include antibiotics (as may usually be recognized by their suffixes, such as -cin, etc.). Although antibiotics are specific inhibitors for certain functions of prokaryotic cells, or bacteria, they may also inhibit biochemical reactions in the eukaryotic cells of mammals, including humans, and can even be toxic, some extremely so. 

The alkaloids listed as inhibitors commonly end in -ine. Many are listed in Appendix E and Appendix F of Hoffman (1999). Alkaloids are inherently toxic to protein synthesis, although some may have beneficial uses, for example, vinblastine, a known anticancer agent for blood-related cancers. 

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The sequences of eukaryotic promoters are more variable than their prokaryotic counterparts (see Fig. 26-8). The three eukaryotic RNA polymerases usually require an array of general transcription factors in order to bind to a promoter. Yet, as with prokaryotic gene expression, the basal level of transcription is determined by the effect of promoter sequences on the function of RNA polymerase and its associated transcription factors. 

Changes in conformation involved in the function of RNA molecules often lead to large changes in molecular size and shape and involve only partially folded conformations, which preclude crystallization. In such cases SAXS has proved to be a useful technique which complements more local structural techniques such as FRET, hydroxy radical footprinting, and others, as it gives a measure of the global changes in size and shape of the molecule. 

The question of the functions of RNA-PolyP complexes needs further investigation. It is probable that the complexing with PolyP enhances the RNA stability. Some evidence has been obtained that in E. coli PolyPs inhibit RNA degradation by degradosome (Blum et al, 1997). 

Let us suppose the user wishes to visualize genes associated with the function of RNA polymerase in N. meningitidis. If more than one genome is loaded, choose... 

Transfer RNA (tRNA). The function of /RNA is to transfer activated amino acids to the ribosome for assembly and incorporation into growing polypeptide chains. tRNA is the smallest of the three types of RNA (about 75 nucleotides). A given tRNA is a specific carrier for only 1 of the 20 amino acids. Before the amino acid can be bound to a tRNA, it must be first activated, or energized, by ATP, its own specific enzyme aminoacyl, tRNA synthetase, and Mn2+ ... 

Name the three stages of RNA synthesis, and list the functions of RNA polymerase in these processes. 

What Crick called the central dogma of molecular genetics says that the function of DNA is to store information and pass it on to RNA. The function of RNA, in turn, is to read, decode, and use the information received from DNA to make proteins. Three fundamental processes take place ... 

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