Messenger RNA (mRNA), transcribed from a gene on a DNA template, carries information that encodes the directions for protein synthesis by ribosomes. Each of the 25,000 to 30,000 genes in the human genome are present in most of your body cells, but each cell expresses only a small fraction of them. Messenger RNA degradation is one of the methods used by cells to regulate which genes are expressed and when.
Levels of Gene Regulation
Gene expression can be regulated at several levels in a cell. Differential gene transcription regulates which genes are allowed to be transcribed into RNA while selective nuclear RNA processing regulates which transcribed RNA can enter the cytoplasm and become messenger RNA. Genes can be regulated any time before, after or during the processes of translation and transcription.
Transcription is the synthesis of messenger RNA from a DNA template. The mRNA created from the process of transcription can leave the nucleus and enter the cytoplasm where it is transcribed by ribosomes to create protein products.
Different messenger RNA are translated at different rates by the cell. Each mRNA differs in the rate at which they are translated into protein and in the stability of the mRNA molecule. The longer-lasting an mRNA molecule is, the more protein products that can be transcribed from the mRNA sequence.
Most bacterial mRNA have a half-life of only a few minutes with bacterial mRNA half-lives varying from less than 1 minute up to 20 minutes. The average half-life of human mRNA is 10 hours with human mRNA half-lives varying between 30 minutes and 24 hours.
While cells degrade messenger RNA to regulate the amount of proteins that can be translated from each mRNA molecule, they also modify mRNA molecules in a way that increases the stability of the molecule and increases the protein output under specific conditions and at certain times. The addition of a polyA tail to the 3' end of an mRNA molecule increases the stability of the mRNA molecule. The longer the polyA tail, the more stable the molecule and the more protein that can be translated.