RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing introns and so joining together exons. For nuclear-encoded genes, splicing occurs in the nucleus either during or immediately after transcription. For those eukaryotic genes that contain introns, splicing is usually needed to create an mRNA molecule that can be translated into protein. For many eukaryotic introns, splicing occurs in a series of reactions which are catalyzed by the spliceosome, a complex of small nuclear ribonucleoproteins (snRNPs). There exist self-splicing introns, that is, ribozymes that can catalyze their own excision from their parent RNA molecule.
A spliceosome is a large ribonucleoprotein (RNP) complex found primarily within the nucleus of eukaryotic cells. The spliceosome is assembled from small nuclear RNAs (snRNA) and numerous proteins. Small nuclear RNA (snRNA) molecules bind to specific proteins to form a small nuclear ribonucleoprotein complex, which in turn combines with other snRNPs to form a large ribonucleoprotein complex called a spliceosome. The spliceosome removes introns from a transcribed pre-mRNA, a type of primary transcript. This process is generally referred to as splicing. An analogy is a film editor, who selectively cuts out irrelevant or incorrect material from the initial film and sends the cleaned-up version to the director for the final cut.
The RNA-induced silencing complex, or RISC, is a multiprotein complex, specifically a ribonucleoprotein, which functions in gene silencing via a variety of pathways at the transcriptional and translational levels. Using single-stranded RNA (ssRNA) fragments, such as microRNA (miRNA), or double-stranded small interfering RNA (siRNA), the complex functions as a key tool in gene regulation. The single strand of RNA acts as a template for RISC to recognize complementary messenger RNA (mRNA) transcript. Once found, one of the proteins in RISC, Argonaute, activates and cleaves the mRNA. This process is called RNA interference (RNAi) and it is found in many eukaryotes; it is a key process in defense against viral infections, as it is triggered by the presence of double-stranded RNA (dsRNA).
Splicing factor U2AF 65 kDa subunit is a protein that in humans is encoded by the U2AF2 gene.
Regulator of nonsense transcripts 1 is a protein that in humans is encoded by the UPF1 gene.
Exosome component 2, also known as EXOSC2, is a protein which in humans is encoded by the EXOSC2 gene.
Gem-associated protein 2 (GEMIN2), also called survival of motor neuron protein-interacting protein 1 (SIP1), is a protein that in humans is encoded by the GEMIN2 gene.
Cleavage stimulation factor 64 kDa subunit is a protein that in humans is encoded by the CSTF2 gene.
Protein argonaute-2 is a protein that in humans is encoded by the EIF2C2 gene.
Protein HEXIM1 is a protein that in humans is encoded by the HEXIM1 gene.
DNA excision repair protein ERCC-8 is a protein that in humans is encoded by the ERCC8 gene.
Voltage-gated potassium channel subunit beta-1 is a protein that in humans is encoded by the KCNAB1 gene.
Cleavage stimulation factor 50 kDa subunit is a protein that in humans is encoded by the CSTF1 gene.
The human ATP5F1C gene encodes the gamma subunit of an enzyme called mitochondrial ATP synthase.
40S ribosomal protein S20 is a protein that in humans is encoded by the RPS20 gene.
Splicing factor 45 is a protein that in humans is encoded by the RBM17 gene.
tRNA-splicing endonuclease subunit Sen34 is an enzyme that in humans is encoded by the TSEN34 gene.
tRNA-splicing endonuclease subunit Sen2 is an enzyme that in humans is encoded by the TSEN2 gene.
tRNA-intron lyase is an enzyme. As an endonuclease enzyme, tRNA-intron lyase is responsible for splicing phosphodiester bonds within non-coding ribonucleic acid chains. These non-coding RNA molecules form tRNA molecules after being processed, and this is dependent on tRNA-intron lyase to splice the pretRNA. tRNA processing is an important post-transcriptional modification necessary for tRNA maturation because it locates and removes introns in the pretRNA. This enzyme catalyses the following chemical reaction:
