Poly(A-U) is a molecular structure composed of a series of adenosine (A) and uridine (U) nucleotides that are connected by phosphodiester bonds. This structure is commonly found at the 3' end of mRNA molecules. "Poly" refers to the polymerization of nucleotides, while "A" and "U" indicate the specific adenosine and uridine bases involved.
This sequence is formed during mRNA processing, a crucial step in gene expression, where a long chain of RNA is synthesized based on the DNA template. After transcription, a series of enzymatic processes, known as post-transcriptional modifications, take place to modify the newly synthesized mRNA. One of these modifications is the addition of the poly(A) tail to the 3' end of the mRNA.
The poly(A) tail, consisting of multiple adenosine nucleotides, plays several important roles in mRNA stability, transport, and translation. It protects mRNA from degradation by exonucleases, helps in the export of mRNA from the nucleus to the cytoplasm, and interacts with ribosomes during translation initiation. The addition of uridine residues to the poly(A) tail in certain cases results in the formation of the poly(A-U) sequence.
Poly(A-U) is also known to be involved in regulating mRNA decay and translation efficiency, influencing the stability and the rate of protein production from mRNA molecules. Furthermore, it participates in the proper recognition of mRNA by cellular machineries and regulatory RNA-binding proteins. Overall, poly(A-U) is a crucial element of mRNA processing and regulation, contributing to the proper functionality and expression of genetic information.
