Nucleases

The expression of genes into protein products requires the generation of a messenger RNA (mRNA) by transcription and the subsequent translation of the mRNA into protein. In bacteria, the mRNA is transcribed, translated, and then degraded by ribonucleases in rapid succession. Thus, the ribonucleases are primarily responsible for mRNA degradation in bacteria. In animal cells, RNA molecules are transcribed as precursors that require processing by ribonucleases to generate functional RNAs. This RNA maturation process requires cleavage by endonucleases and trimming by exonucleases. After the mRNA is translated into protein it is degraded by additional ribonucleases.