Mechanisms for mRNA Degradation

1349 WordsJan 25, 20185 Pages
Messenger RNA (mRNA) is extremely important in expression of protein-coding genes. mRNA molecules contain the genetic code for synthesis of particular polypeptides during translation. (Lewin’s Genes XI, 624) Messenger RNAs are unstable molecules due to the fact that cells have ribonucleases. These ribonucleases can specifically target mRNA molecules in the cytoplasm. There are two types of ribonucleases. Endoribonucleases cut the center of the RNAs, and exoribonuleases detach the ends of RNAs. (Lewin’s Genes XI, 625) The stability of mRNA is essential in controlling gene expression. Less stable RNAs are more likely to undergo changes in transcription rates, and the more stable RNAs are able to go through translation for longer periods of time. (Lewin’s Genes XI, 626) There are several pathways in which mRNAs are degraded. However, the two most common pathways are deadenylation dependent. This means that the degradation process is originated by breaching their protective poly(A) tail. The new poly(A) tail produced is covered in poly(A)-binding proteins (PABP). Certain poly(A) nucleases catalyze the steady shortening of the poly(A) tail as it enters the cytoplasm. The PAN2/3 complex originally shortens the poly(A) tail. Then, CCR4-NOT complex degrades the rest of the poly(A) tail more quickly, only leaving 10 to 12 bases remaining. (Lewin’s Genes XI, 629-30) The first of the two common pathways is the 5’ to 3’ pathway. First, decapping enzymes comprising of

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