A poly-A tail is a chain of adenine nucleotides that gets added to the end of a messenger RNA (mRNA) molecule during a process called mRNA processing. The poly-A tail plays a few important roles. It helps protect the mRNA from being degraded, it assists in the export of the mRNA from the nucleus to the cytoplasm, and it also helps in the translation of the mRNA into proteins. In simpler terms, think of it as a little "hat" that helps the mRNA stay safe and get where it needs to go.