Post-transcriptional control can occur at any stage after transcription, including RNA splicing, nuclear shuttling, and RNA stability. Once RNA is transcribed, it must be processed to create a mature RNA that is ready to be translated. This involves the removal of introns that do not code for protein. Spliceosomes bind to the signals that mark the exon/intron border to remove the introns and ligate the exons together. Once this occurs, the RNA is mature and can be translated.
RNA is created and spliced in the nucleus, but needs to be transported to the cytoplasm to be translated. RNA is transported to the cytoplasm through the nuclear pore complex. Once the RNA is in the cytoplasm, the length of time it resides there before being degraded, called RNA stability, can also be altered to control the overall amount of protein that is synthesized.
The RNA stability can be increased, leading to longer residency time in the cytoplasm, or decreased, leading to shortened time and less protein synthesis. RNA stability is controlled by RNA-binding proteins (RPBs) and microRNAs (miRNAs). These RPBs and miRNAs bind to the 5′ UTR or the 3′ UTR of the RNA to increase or decrease RNA stability. Depending on the RBP, the stability can be increased or decreased significantly; however, miRNAs always decrease stability and promote decay.
3′ untranslated region; region just downstream of the protein-coding region in an RNA molecule that is not translated
a methylated guanosine triphosphate (GTP) molecule that is attached to the 5′ end of a messenger RNA to protect the end from degradation
5′ untranslated region; region just upstream of the protein-coding region in an RNA molecule that is not translated
enzyme that chops the pre-miRNA into the mature form of the miRNA
small RNA molecules (approximately 21 nucleotides in length) that bind to RNA molecules to degrade them
a series of adenine nucleotides that are attached to the 3′ end of an mRNA to protect the end from degradation
RNA-binding protein (RBP)
protein that binds to the 3′ or 5′ UTR to increase or decrease the RNA stability
how long an RNA molecule will remain intact in the cytoplasm
segment of the RNA molecule that are not translated into protein. These regions lie before (upstream or 5′) and after (downstream or 3′) the protein-coding region
protein complex that binds along with the miRNA to the RNA to degrade it