Complementarity with mRNA

The isolation of mRNA also became possible during the years of the decade. The discovery that a large proportion of mRNA species carried polymers of adenylate at their 3 -OH ends enabled the design of affinity chromatography supports such as oligo-dT cellulose and poly-U Sepharose which, because of their complementarity with the poly-A tails of the mRNA, could be employed to purify them from total RNA. These same poly-A tails made the purified mRNAs ideal substrates for reverse transcriptase. Oligomers of deoxythymidine (dT) could hydrogen bond to the poly-A and provide a primer for the initiation of transcription of a cDNA. 

After formation of the initiation dipeptide, the first EF-G-dependent translocation allows binding of the third aminoacyl-tRNA in the A-site so that a tripeptide is formed. The apparent rate of this event may depend upon the nature of the initiation complex initially formed, being slower, for instance, with those containing mRNAs with an extended SD sequence than with those having either very short or no SD complementarity (C. O. G. and M. Rodnina, unpublished results). Furthermore, very powerful translocation inhibitors may block tripeptide formation to such an extent that they mimic translation initiation inhibitors. 

DNA stores the genetic information, while RNA molecules are responsible for transmitting this information to the ribosomes, where protein synthesis actually occurs. This complex process involves, first, the construction of a special RNA molecule called messenger RNA (mRNA). The mRNA is built in the cell nucleus on the appropriate section of DNA (the gene) the double helix is unzipped, and the complementarity of the bases is used in a process similar to that used in DNA replication. The mRNA then migrates into the cytoplasm of the cell where, with the assistance of the ribosomes, the protein is synthesized. 

Kuroda, H. and P. Maliga, Complementarity of the 16S rRNA penultimate stem with sequences downstream of the AUG destabilizes the plastid mRNAs. Nucleic Acids Res, 2001 29(4) 970-975. 

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