Polyadenyleerd

Polyadenyleerd refers to the state of having a polyadenylate tail added to the 3' end of an RNA molecule, most commonly a messenger RNA, during RNA processing. In eukaryotes, polyadenylation is a conserved step in processing pre-mRNA and producing a mature transcript that is ready for export to the cytoplasm.

The process begins with recognition of a polyadenylation signal, typically AAUAAA, upstream of the cleavage site, along with downstream sequence elements. Endonucleolytic cleavage defines the 3' end of the upstream segment. Poly(A) polymerase then adds a stretch of adenosine residues to the new 3' end, forming the poly(A) tail. The tail is bound by poly(A)-binding proteins (PABP), which help protect the transcript, promote nuclear export, and enhance translation initiation.

Polyadenyleerd is functionally important for mRNA stability and translational control. The length of the poly(A) tail can influence the efficiency of translation and may change during development or in response to cellular conditions. In some contexts, cytoplasmic polyadenylation activates the translation of stored mRNAs, particularly in oocytes and early embryos.

Tail length is dynamically regulated by deadenylases and other factors, and degradation pathways remove poly(A) tails as part of mRNA turnover. In bacteria, polyadenylation more often marks RNAs for decay, illustrating divergent roles across domains of life.

Overall, polyadenyleerd describes transcripts that bear a poly(A) tail, a feature central to post-transcriptional gene regulation in many organisms.