High impact information on PRP8

• The PRP8 protein is a component of the U5 snRNP and associates with the U4/U6 snRNAs/snRNP to form a multi-snRNP particle believed to be important for spliceosome assembly [1].
• By using antibodies against the yeast PRP8 protein, a pre-mRNA splicing factor of relative molecular mass 280,000 (Mr280K) stably associated with U5 small nuclear ribonucleoproteins (snRNPs), we have now identified an immunologically related protein in HeLa cell nuclear extracts [2].
• The striking proximity of two of the prp8 suppressor mutations to the site of the 5'SS:hPrp8 cross-link suggests that some protein:5'SS contacts made before the first step may be subsequently extended to accommodate the 3'SS for the second catalytic step [3].
• By isolating mutants that eliminate the normal preference for uridine-containing 3' splice sites in a cis-competition, we identified a mutation that is an allele of PRP8, prp8-101 [4].
• In addition, a suppressor of prp28-1 is a mutant allele of PRP8, which encodes a U5 protein, thus linking PRP28 with U5 [5].

Biological context of PRP8

• We identified one of the suppressors as a missense mutation of PRP8 (R1753K), a protein component of the U5 small nuclear ribonucleoprotein [6].
• The nucleotide sequence of DBF3 turned out to be identical to the yeast gene PRP8, which encodes a U5 snRNP required for pre-mRNA splicing [7].
• Extensive genetic interactions between PRP8 and PRP17/CDC40, two yeast genes involved in pre-mRNA splicing and cell cycle progression [8].
• We show that mutations in the PRP8 gene are able to suppress the temperature-sensitive growth phenotype and the splicing defect conferred by the absence of the Prp17 protein [8].
• We propose that GTP hydrolysis results in a rearrangement between Prp8 and the C terminus of Snu114 that leads to release of U1 and U4, thus activating the spliceosome for catalysis [9].

Anatomical context of PRP8

• PRP8 encodes a highly conserved U5 snRNP protein required for spliceosome assembly and for both catalytic steps of the splicing reaction [8].

Associations of PRP8 with chemical compounds

• Precursor RNAs containing 4-thiouridine at specific sites were used with UV-crosslinking to map the binding sites of the yeast protein splicing factor PRP8 [10].
• In the spliceosome, the Prp40 WW domains participate in cross-intron bridging by interacting with proline-rich regions present in the branch-point binding protein (BBP) and the U5 small nuclear ribonucleoprotein component Prp8 [11].

Physical interactions of PRP8

• These findings suggest a model whereby Prp22 disrupts an RNA/protein or RNA/RNA interaction in the spliceosome that is normally stabilized by Prp8 [6].
• Furthermore, we found that both Prp40 WW domains interact with PPxY motifs (where x is any residue) present in peptides derived from the splicing factors BBP and Prp8 [11].

Other interactions of PRP8

• Moreover, other PRP8 alleles exhibit synthetic lethality with the absence of Prp17p and show a reduced ability to splice an intron bearing an altered 3' splice junction [8].
• Interestingly, deletion of SKY1 was synthetically lethal with all prp17 mutants tested, but only with specific prp8 alleles in a domain implicated in governing fidelity of 3'AG recognition [12].
• A genetic screen for suppressors of BS A-to-G mutants, which stall between the two steps, identified Prp8, the highly conserved spliceosomal factor. prp8 suppressors facilitate the second step for multiple intron mutants and interact functionally with first step suppressors, alleles of PRP16 and U6 snRNA [13].
• Furthermore, additional genetic interactions with U4-cs1 support a two-state model for this RNA conformational switch and implicate another splicing factor, Prp31, in Prp8-mediated spliceosome activation [14].
• PRP8 protein could be UV-crosslinked to pre-mRNA in PRP2-depleted spliceosomes stalled before initiation of the splicing reaction [15].

Analytical, diagnostic and therapeutic context of PRP8

• To analyse at which steps of splicing and with which precursor-derived RNA species the interaction(s) take place, UV-crosslinking was combined with PRP8-specific immunoprecipitation and the coprecipitated RNA species were analysed [15].
• Dissection of Prp8 protein defines multiple interactions with crucial RNA sequences in the catalytic core of the spliceosome [16].

References