3 splice sites

A4. Arredondo-Vega, F. X., Santisteban, I., Kelly, S., Schlossman, C., Umetsu, D and Hershfield, M. S., Correct splicing despite a G- A mutation at the invariant first nucleotide of a 5 splice site A possible basis for disparate clinical phenotypes in siblings with adenosine deaminase (ADA) deficiency. Am. J. Hum. Genet. 54,820-830 (1994). 

K9. Kanno, H., Wei, D. C. C., Miwa, S., Chan, L. C., and Fujii, H., Identification of a 5 -splice site mutation and a missense mutation in homozygous pyruvate kinase deficiency cases found in Hong Kong. Blood 82 (Suppl. 1), 97a (1993). 

N2. Nakajima, H., Kono, N Yamasaki, T Hotta, K., Kawachi, M Kuwajima, M., Noguchi, T., Tanaka, T., and Tarui, S Genetic defect in muscle phosphofructokinase deficiency Abnormal splicing of the muscle phosphofructokinase gene due to a point mutation at the 5 -splice site. J. Biol. Chem. 265, 9392-9395 (1990). 

Santisteban, I., Arredondo-Vega, F. X., Kelly, S., Debre, M., Fischer, A., Pdrignon, J. L., Hilman, B., Eldahr, J., Dreyfus, D. H., Howell, P. L., and Hershfield, M. S Four new adenosine deaminase mutations, altering a zinc-binding histidine, two conserved alanine, and a 5 splice site. Hum. Mutat. 5,243-250 (1995). 

Hutton, M., Lendon, C. L., Rizzu, P. et al. Association of missense and 5 -splice-site mutations in tau with the inherited dementia FTDP-17. Nature 393 702-705,1998. 

The removal of introns from pre-messenger RNAs in eukaryotes is catalyzed by the spliceosome, which is a large ribonucleoprotein consisting of at least 70 proteins and five small nuclear RNAs (snRNA) [144]. This splicing pathway involves two phosphotransfer reactions. In the first step, the 5 splice site is attacked by a 2 hydroxy group of an adenosine nucleotide within the intron [indicated by A in Fig. 12] that corresponds to the branch point in the lariat intermediate (Fig. 12,middle). In the second step, the 3 -OH group of the free 5 exon attacks the phosphodiester bond between the intron and... 

Fig. 12 The spliceosome splicing reaction. In the first step, the 2 -OH of an adenosine residue that is conserved in the intron attacks the phosphorus at the 5 splice site and generates an intron-3 -exon 2 intermediate and a free 5 exon 1. In the second step, the free 3 -OH of the 5 exon attacks the phosphorus at the 3 splice site to produce ligated exons and an excised intron...

Of the five snRNAs, U2 and U6 interact with the reaction site (the 5 splice site and the branch point) in the first chemical step. These two snRNAs are known to anneal together to form a stable-based paired structure in the absence of proteins and in the presence of ions as shown in Fig. 13, with U2 acting as an inducer molecule that displaces the U4 (that is an antisense molecule that regulates the catalytic function of U6 RNA) from the initially formed U4-U6 duplex. The secondary (or higher ordered) structure of the U2-U6 complex consists of the active site of the spliceosome. Recent data suggests that these two snRNAs function as the catalytic domain of the spliceosome that catalyzes the first step of the splicing reaction [145]. 

Fig. 15A,B Modified motif of the adenovirus pre-mRNA substrates studied by Son-theimer et al. [151] A in the Ad5-lS, the guanosine at 5 splice site position was substituted by 2 -deoxy-3 -thiouridine B in the Ad3-lS, the guanosine at 3 splice site position was substituted by 3 -thioinosine...

In the microorganismTetrahymena, group I intron splicing is accomplished in the catalytic cycle shown in Fig. 2. The intron first binds guanosine or one of its 5 -phos-phorylated derivatives which is then used as a nucleophile in cleaving the 5 splice site. 

DLC-B DLC-B MALT MALT 199 Exon 7 Intron 7 (3 splice site) Intron 8 (5 splice site) Intron 8 (5 splice site)... 

Fig. 1.47. Signal sequences for splicing. A splice site is determined by sequences on the 5 side of an intron (5 splice site) and on the 3 side of an intron (3 sphce site).

Horowitz, D.S. and Krainer, A.R. Mechanisms for selecting 5 splice sites in mammalian pre-mRNA splidng. (1994) Trends Genet 10, 100-6... 

Spliceosomal introns generally have the dinucleotide sequence GU and AG at the 5 and 3 ends, respectively, and these sequences mark the sites where splicing occurs. The Ul snRNA contains a sequence complementary to sequences near the 5 splice site of nuclear mRNA introns (Fig. 26-16a), and the Ul snRNP... 

The 2 OH of a specific adenosine in the intron acts as a nucleophile, attacking the 5 splice site to form a lariat structure. 

Splice site 3 Splice sites Poly(A) site... 

The RNA world hypothesis requires a nucleotide polymer to reproduce itself. Can a ribozyme bring about its own synthesis in a template-directed manner The self-splicing rRNA intron of Tetrahymena (Fig. 26-26) catalyzes the reversible attack of a guanosine residue on the 5 splice junction (Fig. 26-37). If the 5 splice site and the internal guide sequence are removed from the intron, the rest of the intron can bind RNA strands paired with short oligonucleotides. Part of the remaining intact intron effectively acts as a template for the... 

Figure 28-22 Assembly and action of the spliceosomal complex. Four special sequence elements control the process the 5 and 3 splice sites, the branch point (adenosine A), and a polypyrimidine tract. The snRNP particle U1 locates the 5 splice site and U2 the branch point. The tri-snRNP U4 U6 U5 then binds, U6 recognizing the 5 splice site, and U1 and U4 are released. The 2 -OH of the branch point adenosine attacks the phos-phodiester linkage to form a lariet intermediate, which releases the intron in a lariet form in the final step. After Valcarcel and Green.612...

After the U1 snRNP binds to the pre-mRNA (step a, Fig. 28-22)614 the U2 snRNP binds to another almost invariant sequence CURACU found 20 to 55 nucleotides upstream of the 3 junction.608,615-617 The A in this sequence becomes a branch point. It is brought close to the 5 splice site with the aid of a preassembled complex of snRNPs U4, U6, and U5. In this complex U4 and U6 are tightly paired, additional proteins are also present,618 21 and enhancers may be located in adjacent exons.617 Upon binding of U6 to the 5 splice site, the U1 and U4 snRNPs are released (step b, Fig. 28-22) and the 2 -OH of the branch point adenosine attacks the backbone phosphorus atom (step c) at the 5 splice junction forming a lariat intermediate. The 3 end created at the 5 junction must now be held and brought close to the 3 splice junction, which is located with the aid of U5 snRNP.622 The 3 splice junction, utilized in the second splicing step (step d, Fig. 28-22) has the consensus sequence (T/C)N(C/T)AG G. 

Yeast protein L30, which is not homologous to any bacterial protein, controls its own synthesis by a feedback inhibition at the mRNA splicing step. L30 binds to its own pre-mRNA near the 5 splice site, blocking completion of the spliceosome assembly (Chapter 28).159... 

The mechanism of self-splicing in this case is somewhat different from that observed in the spliceosome reaction (fig. 28.21). First the 3 hydroxyl group of the guanosine cofactor attacks the phosphodiester bond at the 5 splice site. This is followed by another transesterification reaction in which the 3 hydroxyl group of the upstream RNA attacks the phosphodiester bond at the 3 splice site, thereby completing the splicing reaction. The final reaction products include the spliced rRNA and the excised oligonucleotide. 

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