Protein synthesis read-through translation

If termination codons are not recognized efficiently by termination factors, synthesis continues past the termination codons and new longer protein chains are made. This read-through translation may sometimes be accidental, but it is also used by cells to form several important proteins. For example, the 14-kDa coat protein of bacteriophage Qp is elongated by read-through during translation of the RNA about 4% of the time. This produces a 38-kDa protein known as Ay which has an extra 200 amino acid residues at the C terminus and is essential for formation of infectious virus particles. 

FIGURE 11.1 The fundamental process of information transfer in cells. Information encoded in the nucleotide sequence of DNA is transcribed through synthesis of an RNA molecule whose sequence is dictated by the DNA sequence. As the sequence of this RNA is read (as groups of three consecutive nucleotides) by the protein synthesis machinery, it is translated into the sequence of amino acids in a protein. This information tmiisfer system is encapsulated in the dogma DNA RNA protein. 

Most translation is terminated at this stop codon, but frameshifting, which is induced by a high polyamine concentration, allows read-through and synthesis of the antizyme protein. In rare cases frameshifting may lead to translational bypass of some codons on the mRNA. Such a case is found in a bacteriophage T4 mRNA for which the E. coli ribosomes bypass 50 nucleotides in order to complete the synthesis of a... 

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