Disease relevance of Psi

• A mutant transgene that lacks the PSI-U1 snRNP-interaction domain restores viability but shows courtship behavior abnormalities and meiosis defects during spermatogenesis, resulting in a complete male sterility phenotype [1].

High impact information on Psi

• Here, we report that the conserved U1 snRNP-interacting RNA-binding protein PSI is essential for Drosophila viability [1].
• One specific target, the hrp40/squid transcript, shows an altered pre-mRNA splicing pattern in PSI mutant testes [1].
• A null PSI mutation is recessive lethal at the first-instar larval stage, and lethality is fully rescued by transgenes expressing the PSI protein [1].
• The alternative splicing factor PSI regulates P-element third intron splicing in vivo [2].
• The soma-specific expression pattern of PSI suggests that its low abundance in the germ line allows IVS3 splicing [2].

Biological context of Psi

• Using a construct containing only the RNA binding domain of PSI (PSI-KH03), we introduced a physiologically relevant point mutation into each KH domain of PSI individually and measured stability and RNA binding affinity of the resulting mutant proteins [3].
• We demonstrate that ectopic expression of PSI in the female germ line is sufficient to repress splicing of an IVS3 reporter transgene [2].
• In the HA strain, the Psi values were significantly less and values of R and percent oviposition in photophase were significantly more than those of the LA strain at each level of light intensity [4].
• Alignment of high affinity PSI-binding RNAs revealed a degenerate consensus sequence consisting of a short core motif of CUU flanked by alternative purines and pyrimidines [5].
• To identify high affinity binding sites for the PSI protein, in vitro selection (SELEX) was performed using a random RNA oligonucleotide pool [5].

Associations of Psi with chemical compounds

• FWD1 was shown to recognize the conserved DSGPsiXS motif (where Psi represents the hydrophobic residue) present in the NH(2)-terminal regions of these three IkappaB proteins only when the component serine residues are phosphorylated [6].
• The transition from PSI to early metamorphic phase (PS2 and upwards), induced by rapid elevation in endogenous steroid hormone ecdysone, is accompanied by continuous growth of granule diameter with concomitant reduction in their number per cell [7].

Other interactions of Psi

• These data show that the processing of specific target transcripts, such as the P-element mRNA, is regulated by a functional PSI-U1 snRNP interaction in Drosophila [8].
• P-element somatic inhibitor (PSI) is a KH domain-containing splicing factor highly expressed in Drosophila somatic tissues [8].
• The results indicate that PSI is an alternative splicing factor that regulates tissue-specific splicing, probably through interactions with generally expressed factors such as hrp48 [9].

Analytical, diagnostic and therapeutic context of Psi

• Sequence analysis of cDNAs encoding PSI reveals three KH RNA-binding domains, a conserved motif also found in the yeast splicing regulator MER1 [10].

References