Disease relevance of RNU2P2

• Adenovirus type 12 (Ad12) infection of human cells induces four chromosomal fragile sites corresponding to the U1 small nuclear RNA (snRNA) genes (the RNU1 locus), the U2 snRNA genes (RNU2), the U1 snRNA pseudogenes (PSU1), and the 5S rRNA genes (RN5S) [1].

High impact information on RNU2P2

• U2 as well as U1 small nuclear ribonucleoproteins are involved in premessenger RNA splicing [2].
• We report here the assignment, by in situ hybridization, of the U2 gene cluster to chromosome 17, bands q21-q22 [3].
• As is typical of mammalian snRNAs, human U1 and U2 are each encoded by a multigene family [3].
• Purified complexes contained stoichiometric amounts of U1, U2 and pre-mRNA, and crosslinking studies indicated that these form concomitant base pairing interactions with one another [4].
• Concerted evolution of the tandemly repeated genes encoding human U2 snRNA (the RNU2 locus) involves rapid intrachromosomal homogenization and rare interchromosomal gene conversion [5].

Biological context of RNU2P2

• Although the coding region for the mature form of U2 RNA was only 188 base pairs (bp) long, the basic repeating unit of the tandem array was 6 kilobase pairs in length [6].
• We found that the genes for human U2 small nuclear RNA (snRNA) are organized as a nearly perfect tandem array of 10 to 20 copies per haploid genome [6].
• We found only two polymorphisms within the U2 repeat unit: a SacI polymorphism (alleles SacI+ or SacI-) and a CT microsatellite polymorphism (alleles CT+ or CT-) [5].
• Thus concerted evolution of the U2 tandem array occurs in situ along a chromosome lineage, and linkage disequilibrium between sequences flanking the U2 array may persist for long periods of time [5].
• We propose that the primary driving force for concerted evolution of the tandem U2 genes is intrachromosomal homogenization; interchromosomal genetic exchanges are much rarer, and reciprocal nonsister chromatid exchange apparently does not occur [5].

Anatomical context of RNU2P2

• These data suggest further that the 17S form is the functionally active form of U2 snRNP in the spliceosome [7].
• A set of 5' deletions was constructed and assayed for the ability to direct initiation of U2 snRNA after microinjection into Xenopus oocytes [8].
• The gene cluster for human U2 RNA has been mapped to chromosome 17q21 by in situ hybridization and hybridization analysis of DNA from mouse/human somatic cell hybrids [9].
• When incubated in reactions containing extracts from HeLa cells, these 5-FU U2 RNAs are assembled into RNPs that are recognized by anti-Sm monoclonal antibody even when there is a complete replacement of uridine with 5-FU [10].

Associations of RNU2P2 with chemical compounds

• The microsatellite sequence (CT)n x (GA)n promotes stable chromosomal integration of large tandem arrays of functional human U2 small nuclear RNA genes [11].
• Induction of fragility at the human RNU2 locus by cytosine arabinoside is dependent upon a transcriptionally competent U2 small nuclear RNA gene and the expression of p53 [12].
• Deletion analysis of the 40K protein demonstrated the leucine repeats, including the 40K-specific, seventh repeat, to be essential for specific U2 RNP assembly, most likely through their role as an interface for protein-protein interaction [13].
• The resultant U2 snRNP particle migrates exceptionally slowly in polyacrylamide gels, suggestive of a disorganized structure [14].
• The 7-methylguanosine cap, stem-loops I and II, the lariat branch site recognition sequence, the conserved Sm domain, and several other regions throughout the 5' end of U2 RNA have no apparent role in the 3' processing reaction [15].

Regulatory relationships of RNU2P2

• We demonstrate that the RNU2 locus is sensitive to the drug and that araC-induced fragility is dependent upon a functional U2 gene and on the expression of the cellular p53 protein [12].
• We found that the minimal U1 genes were efficiently expressed and were as effective as minimal U2 genes in generating a novel Ad12-inducible fragile site [16].

Other interactions of RNU2P2

• The p53 gain of function could interfere with chromatin condensation either by blocking mitotic shutdown of U1 and U2 snRNA transcription or by phenocopying global or local DNA damage [1].
• In addition, the natural U1 tandem repeat unit exceeds 45 kb, whereas the U2 tandem repeat unit is only 6.1 kb [16].
• Using a combination of field inversion gel electrophoresis and polymerase chain reaction, we have been able to study the CT microsatellites within individual U2 tandem arrays [17].

Analytical, diagnostic and therapeutic context of RNU2P2

• Using ectopic integration of engineered DNA arrays to create "new" fragile sites, we and others have previously shown that the transcriptionally competent U2 gene is necessary and sufficient for induction of fragility at the RNU2 locus upon infection of human cells with Adenovirus 12 [12].
• Cell enucleation and aqueous cell fractionation are used to prepare nuclear and cytoplasmic fractions and the U1- and U2-specific proteins are identified by isotopic labeling and immunoprecipitation or by immunoblotting with specific autoimmune antisera [18].
• However, when the in vitro assembled U2 snRNPs are subjected to buoyant density gradient centrifugation, the particles that contain 100% 5-FU are not resistant to salt dissociation [10].
• When the in vitro assembled U2 snRNPs were analyzed by velocity sedimentation gradient centrifugation, 5-FU incorporation correlated with a shift in the sedimentation rate of the particles [10].

References