ⓘ RNA splicing ..

Internal loop

Internal-loops in RNA are found where the double stranded RNA separates due to no Watson-Crick base pairing between the nucleotides. Internal-loops differ from Stem-loops as they occur in middle of a stretch of double stranded RNA. The non-canonicoal residues result in the double helix becoming distorted due to unwinding, unstacking and kinking. Internal-loops can be classified as either symmetrical or asymmetrical, with some asymmetrical internal-loops, also known as bulges. Many important structural motifs are composed of internal loops such as the C-loop, the docking-elbow, kink-turns k ...

Splicing regulatory element

Splicing regulatory element are cis -acting sequences in pre-mRNA, which either enhance or silence the splicing of introns, or in general regulates the constitutive or alternative splicing of this pre-mRNA. SREs recruit trans -acting splicing factors to activate or suppress the splice site recognition or spliceosome assembly. The "context dependence" of SREs is categorized into at least two studied groups: the location-dependent activity of SREs: the activity varies with the relative positions of SREs in pre-mRNA; the gene-dependent activity of SREs: the SRE activity observed in one gene i ...

U1 spliceosomal RNA

U1 spliceosomal RNA is the small nuclear RNA component of U1 snRNP, an RNA-protein complex that combines with other snRNPs, unmodified pre-mRNA, and various other proteins to assemble a spliceosome, a large RNA-protein molecular complex upon which splicing of pre-mRNA occurs. Splicing, or the removal of introns, is a major aspect of post-transcriptional modification, and takes place only in the nucleus of eukaryotes.

U2 spliceosomal RNA

U2 spliceosomal snRNAs are a species of small nuclear RNA molecules found in the major spliceosomal machinery of virtually all-eukaryotic organisms. In vivo, U2 snRNA along with its associated polypeptides assemble to produce the U2 small nuclear ribonucleoprotein, an essential component of the major spliceosomal complex. The major spliceosomal-splicing pathway is occasionally referred to as U2 dependent, based on a class of Sm intron - found in mRNA primary transcripts - that are recognized exclusively by the U2 snRNP during early stages of spliceosomal assembly. In addition to U2 depende ...

U4 spliceosomal RNA

The U4 small nuclear Ribo-Nucleic Acid is a non-coding RNA component of the major or U2-dependent spliceosome – a eukaryotic molecular machine involved in the splicing of pre-messenger RNA. It forms a duplex with U6, and with each splicing round, it is displaced from the U6 snRNA in an ATP-dependent manner, allowing U6 to re-fold and create the active site for splicing catalysis. A recycling process involving protein Brr2 releases U4 from U6, while protein Prp24 re-anneals U4 and U6. The crystal structure of a 5′ stem-loop of U4 in complex with a binding protein has been solved.

U6 spliceosomal RNA

U6 snRNA is the non-coding small nuclear RNA component of U6 snRNP, an RNA-protein complex that combines with other snRNPs, unmodified pre-mRNA, and various other proteins to assemble a spliceosome, a large RNA-protein molecular complex that catalyzes the excision of introns from pre-mRNA. Splicing, or the removal of introns, is a major aspect of post-transcriptional modification and takes place only in the nucleus of eukaryotes. The RNA sequence of U6 is the most highly conserved across species of all five of the snRNAs involved in the spliceosome, suggesting that the function of the U6 s ...

U7 small nuclear RNA

The U7 small nuclear RNA is an RNA molecule and a component of the small nuclear ribonucleoprotein complex. The U7 snRNA is required for histone pre-mRNA processing. The 5 end of the U7 snRNA binds the HDE histone downstream element, a conserved purine-rich region, located 15 nucleotides downstream the histone mRNA cleavage site. The binding of the HDE region by the U7 snRNA, through complementary base-pairing, is an important step for the future recruitment of cleavage factors during histone pre-mRNA processing.

U11 spliceosomal RNA

The U11 snRNA is an important non-coding RNA in the minor spliceosome protein complex, which activates the alternative splicing mechanism. The minor spliceosome is associated with similar protein components as the major spliceosome. It uses U11 snRNA to recognize the 5 splice site while U12 snRNA binds to the branchpoint to recognize the 3 splice site.

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