Published on: Mar 4, 2016
Transcripts - Polyadenylation
Name – Anjali Krishnan, Department of Botany
Most eukaryotic mRNA undergoes a quite complicated series
of modification and processing events before translation
Removal of introns .
Polyadenylation is the addition of a poly(A) tail to
a messenger RNA.
The poly(A) tail consists of multiple adenosine
monophosphates; in other words, it is a stretch of RNA that
has only adenine bases.
In eukaryotes, polyadenylation is part of the process that
produces mature messenger RNA (mRNA) for translation.
It, therefore, forms part of the larger process of gene
The poly(A) tail is important for the nuclear export,
translation, and stability of mRNA. The tail is shortened
over time, and, when it is short enough, the mRNA is
enzymatically degraded. However, in a few cell types,
mRNAs with short poly(A) tails are stored for later
activation by re-polyadenylation in the cytosol .In contrast,
when polyadenylation occurs in bacteria, it promotes RNA
degradation. This is also sometimes the case for
eukaryotic non-coding RNAs.
mRNA molecules in both prokaryotes and eukaryotes
have polyade9nylated 3'-ends, with the prokaryotic
poly(A) tails generally shorter and less mRNA
Termination of transcription occurs only after RNA
polymerase has transcribed past a consensus AAUAAA
sequence - the poly(A)+ addition site
10-30 nucleotides past this site, a string of 100 to 200
adenine residues are added to the mRNA transcript -
the poly(A)+ tail
poly(A) polymerase adds these A residues
Function not known for sure, but poly(A) tail may
govern stability of the mRNA
iGenetics - Peter j. Russell
Genetics – P.S. Verma