title: Nuclear Speckle-related Protein 70 Binds to Serine/Arginine-rich Splicing Factors 1 and 2 via an Arginine/Serine-like Region and Counteracts Their Alternative Splicing Activity.
abstract: Nuclear speckles are subnuclear storage sites containing pre-mRNA splicing machinery. Proteins assembled in nuclear speckles are known to modulate transcription and pre-mRNA processing. We have previously identified nuclear speckle-related protein 70 (NSrp70) as a novel serine/arginine (SR)-related protein that co-localizes with classical SR proteins such as serine/arginine-rich splicing factor 1 (SRSF1 or ASF/SF2) and SRSF2 (SC35). NSrp70 mediates alternative splice site selection, targeting several pre-mRNAs, including CD44 exon v5. Here we demonstrated that NSrp70 interacts physically with two SR proteins, SRSF1 and SRSF2, and reverses their splicing activity in terms of CD44 exon v5 as exon exclusion. The NSrp70 RS-like region was subdivided into three areas. Deletion of the first arginine/serine-rich-like region (RS1) completely abrogated binding to the SR proteins and to target mRNA and also failed to induce splicing of CD44 exon v5, suggesting that RS1 is critical for NSrp70 functioning. Interestingly, RS1 deletion also resulted in the loss of NSrp70 and SR protein speckle positioning, implying a potential scaffolding role for NSrp70 in nuclear speckles. NSrp70 contains an N-terminal coiled-coil domain that is critical not only for self-oligomerization but also for splicing activity. Consistently, deletion of the coiled-coil domain resulted in indefinite formation of nuclear speckles. Collectively, these results demonstrate that NSrp70 acts as a new molecular counterpart for alternative splicing of target RNA, counteracting SRSF1 and SRSF2 splicing activity.
authors.affiliation: From the School of Life Sciences, Immune Synapse Research Center, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Chang-Hyun
authors.initials: CH
authors.lastname: Kim
authors.affiliation: the Stem Cell Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahak-ro, Yuseng-gu, Daejeon 3414, Korea, and.
authors.forename: Young-Dae
authors.initials: YD
authors.lastname: Kim
authors.affiliation: From the School of Life Sciences, Immune Synapse Research Center, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Choi
authors.affiliation: From the School of Life Sciences, Immune Synapse Research Center, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Hye-Ran
authors.initials: HR
authors.lastname: Kim
authors.affiliation: From the School of Life Sciences, Immune Synapse Research Center, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea.
authors.forename: Bo-Ra
authors.initials: BR
authors.lastname: Na
authors.affiliation: the Academy of Immunology and Microbiology, Institute for Basic Science, and Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea.
authors.forename: Sin-Hyeog
authors.initials: SH
authors.lastname: Im
authors.affiliation: From the School of Life Sciences, Immune Synapse Research Center, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea, cdjun@gist.ac.kr.
authors.forename: Chang-Duk
authors.initials: CD
authors.lastname: Jun
mesh_terms: D017398:Alternative Splicing; D057809:HEK293 Cells; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D012322:RNA Precursors / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism*; D000068103:Serine-Arginine Splicing Factors / Q000378:metabolism*
chemical_list: C497483:CD44 protein, human; D018960:Hyaluronan Receptors; C560091:NSRP1 protein, human; D009687:Nuclear Proteins; D020033:Protein Isoforms; D012322:RNA Precursors; D012261:Ribonucleoproteins; C000595779:SRSF1 protein, human; C073288:SRSF2 protein, human; D000068103:Serine-Arginine Splicing Factors
keywords: CD44; NSrp70; RNA binding protein; RS-like region; SR protein; alternative splicing; coiled-coil domain; dimerization; heterogeneous nuclear ribonucleoprotein (hnRNP); nuclear speckle