Diversity of Vertebrate Splicing Factor U2AF35

Abstract

35 b varies from 10-fold in the brain to 20-fold in skeletal muscle. We propose that post-transcriptional regulation of U2AF1 gene expression may provide a mechanism by which the relative cellular concentration and availability of U2AF 35 protein isoforms are modulated, thus contributing to the finely tuned control of splicing events in different tissues.In higher eukaryotes, most protein-coding genes contain sequences that are spliced from the nascent transcripts (pre-mRNAs) in the nucleus. Intron excision is carried out by an assembly of small nuclear RNAs and proteins that are collectively recruited to pre-mRNAs forming the spliceosome (reviewed in Ref. 1). Although introns are excised with a high degree of precision, for many pre-mRNAs there is flexibility in the choice of alternative splice sites, often in response to tissuespecific, physiologically or developmentally regulated states. Alternative splicing produces multiple mRNAs encoding distinct proteins, thus expanding the coding capacity of genes and contributing to the proteomic complexity of higher organisms (2-4). Moreover, alternative splicing may contribute to regulate protein expression by generating premature termination codons that target the transcript to nonsense-mediated mRNA decay (5).In metazoans, pre-mRNA sequences implicated in splicing are only weakly conserved. Multiple, relatively weak proteinprotein and protein-RNA interactions involving these sequences and additional regulatory sequence elements, which can positively or negatively affect spliceosome assembly at nearby splice sites, constitute the basis to control alternative splicing (for recent reviews see Refs. 4, 6, and 7). Proteins that bind to pre-mRNA and affect splicing regulation include SR proteins, hnRNPs, 1 and tissue-or developmental stage-specific factors. Individual SR proteins interact only weakly with enhancer elements, but their binding to pre-mRNA is highly cooperative and can lead to recognition of distinct RNA sequence motifs, thus contributing to the selection of regulated splice sites. A distinct role is played by hnRNP proteins, which in general antagonize the stimulatory activity of SR proteins, and cell type-specific proteins, which may either inhibit or promote splicing. Thus, control of alternative splicing is achieved through the combinatorial interplay of both regulatory sequence signals and trans-acting protein factors (4,8,9).The spliceosome is a multicomponent RNA-protein machine containing five uracil-rich small nuclear ribonucleoproteins (U snRNPs) and many non-snRNP protein splicing factors. In the late 1990s ϳ100 splicing factors were identified (10), and since then the number has nearly doubled (1). Initiation of spliceosome recruitment to a pre-mRNA involves recognition of the 5Ј splice site by the U1 snRNP, whereas the U2 snRNP associates with the 3Ј region of the intron. The establishment of a stable interaction between U2 snRNP and pre-mRNA requires an auxiliary factor, U2AF (11). The U2

The Production of Transgenic Mice Expressing Human Cystathionine Beta-Synthase to Study Down Syndrome

“…The locations of the insert ends of P102D1 were determined by end sequencing and BLAST analysis of the human genome (Altschul et al, 1990). This analysis showed that P102D1 contains CBS and also U2AF1, an RNA splicing factor (Hattori et al, 2000: Pacheco et al, 2004. Because P102D1 contains the U2AF1 gene in addition to the CBS gene, Nhe1 restriction sites were identified in the P102D1 insert that bracket a 60,452 bp segment containing the complete human CBS gene but not the 5¢ end of the U2AF1 gene.…”

The (In)dependence of Alternative Splicing and Gene Duplication

“…Interestingly, several recent studies point to a direct equivalence between AS and GD. There are some cases where alternative splice variants in one organism are similar to gene duplicates in another organism [6–9]. For example, the eukaryotic splicing factor U2AF35 has at least two functional splice variants in human, U2AF35a and U2AF35b, which differ by seven amino acids in the RNA recognition motif (Figure 1A).…”

Analysis of Mutant Phenotypes and Splicing Defects Demonstrates Functional Collaboration between the Large and Small Subunits of the Essential Splicing Factor U2AF In Vivo

“…Indeed, inhibition of Drosophila msl-2 splicing by Sex-lethal appears to rely on an unusually long branchpoint to 3Ј splice site distance to allow the alternative splicing factor to displace U2AF (Merendino et al, 1999). In addition, the presence in metazoans of genes related to the hsU2AF small subunit (Tronchere et al, 1997;Mount and Salz, 2000;Tupler et al, 2001;Pacheo et al, 2004) as well as tissue-specific alternatively spliced isoforms (Pacheo et al, 2004) suggests the possibility of modular hsU2AF function, wherein 3Ј splice site recognition depends on the attributes of different heterodimeric partners for hsU2AF LG .Collectively, the data from a variety of studies in metazoans and both budding and fission yeast suggest that, unlike the evolutionarily conserved process of 5Ј splice site recruitment via complementary base-pairing to U1 snRNA, the interplay between cis-acting elements and trans-acting factors during initial recognition of the 3Ј splice site has diverged significantly during evolution. …”