Disease relevance of SFRS2

• The SR protein SC35 is responsible for aberrant splicing of the E1alpha pyruvate dehydrogenase mRNA in a case of mental retardation with lactic acidosis [1].
• Identification of a domain in human immunodeficiency virus type 1 rev that is required for functional activity and modulates association with subnuclear compartments containing splicing factor SC35 [2].
• The same distribution of HIV-1 RNAs relative to SC-35 was also seen in transfected HeLa cells and in primary human lymphocytes infected with HIV-1 primary isolates [3].
• Mutation analysis of a putative sialyltransferase gene, the SFRS2 splicing factor gene and the c-myb ET-locus in two families with hereditary neuralgic amyotrophy (HNA) [4].
• HMGA1a expression was induced by hypoxia and the protein was accumulated in the nuclear speckles with the endogenous splicing factor SC35 [5].

High impact information on SFRS2

• These SR proteins, which include SC35 and SF2/ASF, are conserved from Drosophila to man, are required for early steps of spliceosome assembly and can influence splice-site selections [6].
• I report here that SC35 was sufficient on its own to form a committed complex with human beta-globin pre-mRNA [6].
• Spliceosome assembly factor SC-35 localized within the center of individual domains [7].
• A search of the DNA sequence database revealed that the thymus-specific exon (ET) of the c-myb proto-oncogene is encoded on the antisense strand of the SC35 gene [8].
• We present evidence, based on both in vivo and in vitro experiments, that the skipping of this exon is due to the disruption of an SC35-dependent splicing enhancer within exon 51 [9].

Biological context of SFRS2

• Using a score-matrix analysis to identify putative exonic enhancer sequences (ESEs), we found multiple high score ESE motifs for SF2/ASF, SC35, and SRp40 in exon 3 of G alpha(s) [10].
• Moreover, cross-linking experiments show that both ASF/SF2 and SC35 are able to displace binding of hnRNP A1 to the G-rich element, suggesting that the binding sites for these proteins are overlapping [11].
• This gene spans 7745 nucleotides and consists of 8 exons and 7 introns within the coding sequence, thus contrasting with the organization of the SC35/PR264 or RBP1 SR genes [12].
• SC35 belongs to the family of SR proteins that regulate alternative splicing in a concentration-dependent manner in vitro and in vivo [13].
• Furthermore, in cultured cells, SC35 overexpression increases apoptosis; whereas heterogeneous nuclear ribonucleoprotein A1 overexpression decreases apoptosis [14].

Anatomical context of SFRS2

• The results showed a decrease of snRNPs and SC-35 in the karyoplasm as the oocytes progress from a transcriptionally active to the inactive state [15].
• Here, we show that overexpression of SC35 in HeLa cells results in a significant decrease of endogenous SC35 mRNA levels along with changes in the relative abundance of SC35 alternatively spliced mRNAs [13].
• Consistently, ectopic overexpression of this splicing factor enhanced the use of the cryptic splice site, whereas small interfering RNA-mediated reduction of the SC35 protein levels in primary fibroblasts from the patient resulted in the almost complete disappearance of the aberrantly spliced E1alpha PDH mRNA [1].
• On account of the SC35-immunostaining patterns no distinction of subpopulations of astrocytes is possible [16].
• Transient transfection of the U1 snRNP 70K protein into COS cells induced nuclear reorganization and redistribution of the splicing factor SC-35, whereas hnRNP proteins were not affected [17].

Associations of SFRS2 with chemical compounds

• CIR was found to be colocalized with SC35 and PAP-1 in nuclear speckles [18].
• Actinomycin D treatment caused the relocalisation of alpha B-crystallin along with Sm and SC35 to a smaller number of more distinct spots, suggesting a link between speckle localisation and the transcriptional status of the cells [19].
• The human pre-mRNA splicing factors SF2 and SC35 have similar electrophoretic mobilities, and both of them contain an N-terminal ribonucleoprotein (RNP)-type RNA-recognition motif and a C-terminal arginine/serine-rich domain [20].
• While a subset of serine/arginine protein splicing factors, including SF2/ASF, SC35, and SRp20, is efficiently recruited to the tau gene when exon 10 is included, these factors are less frequently associated with tau transcription sites when exon 10 is excluded [21].
• Affinity-purified antibodies eluted from recombinant proteins recognized a 64-kD nuclear protein in Western blotting and decorated the nucleoplasm in a speckled-network fashion in immunofluorescence, colocalizing with antibodies to pre-mRNA splicing factor SC35 and uridine-rich small nuclear RNAs [22].

Co-localisations of SFRS2

• Cyclin L2 interacted with splicing factor 2 in vitro and was co-localized with the splicing factor SC35 in the nuclear speckle compartment [23].

Other interactions of SFRS2

• We conclude that exon 6A recognition in vitro depends on the ratio of the ASF/SF2 to SC35 SR proteins [24].
• This similarity was confirmed by the fact that purified human SC35 also rescues the 9G8-depleted extract [25].
• The distribution of two splicing components (snRNP and SC-35) and coilin were studied by immunogold/electron microscopy in human oocytes from antral follicles at different levels of transcriptional activity (i.e., active, intermediate, and inactive) [15].
• In addition, transiently expressed intron-containing beta-globin RNAs were shown to distribute to weak anti-SC-35 staining in a manner similar to that of HIV-1 RNAs [3].
• The molecular cloning of a 4.1 cDNA encoding the isoform designated 4.1E has allowed us to show that this protein is targeted to the nucleus, that it associates with the splicing factor U2AF35, and that its overexpression induces the redistribution of the splicing factor SC35 [26].

Analytical, diagnostic and therapeutic context of SFRS2

• Double immunofluorescence studies showed that the pseudophosphorylation mutants localized in nuclear speckles containing the splicing factor SC35 [27].
• RT-PCR analysis revealed a marked induction of SC35 and ASF/SF2 as well as mRNA levels in malignant ovarian tissue [28].
• UV cross-linking assays followed by immunoprecipitation with anti-SR protein monoclonal antibodies showed that ESEwt, but not mutated ESE RNA, was able to bind both alternative splicing factor/splicing factor 2 and SC35 [29].
• Examination of Mta localization in transfected cells by indirect immunofluorescence revealed that Mta colocalized with the splicing factor SC35 [30].
• For this reason we used the TUNEL technique in combination with a label for RNA synthesis and splicing factor (SC-35) [31].

References