Involvement of splicing factor-1 in beta-catenin/T-cell factor-4-mediated gene transactivation and pre-mRNA splicing.
OBJECTIVE
beta-Catenin is the downstream effector of the Wnt signaling pathway and is involved in the process of colorectal carcinogenesis. However, it is still uncertain whether beta-catenin exerts its oncogenic function solely by coactivating the target genes of T-cell factor-4 (TCF4). We previously reported that the beta-catenin/TCF4 complex contains several classes of RNA-binding proteins and regulates the premessenger RNA splicing reaction, but the identity of the exact effector molecule downstream of the beta-catenin/TCF4 complex has not been established.


METHODS
Using isotope-coded affinity tagging and mass spectrometry, we examined more than 4000 peptides derived from colorectal cancer cells and identified that splicing factor-1 (SF1) was one of the proteins whose expression is regulated by the beta-catenin/TCF4 complex.


RESULTS
The expression of SF1 was found to be correlated with the differentiation status of intestinal epithelial cells and inversely correlated with tumorigenesis. Immunoprecipitation and immunofluorescence microscopy revealed that SF1 was a complex, and beta-catenin-evoked gene transactivation and cell proliferation were negatively regulated by SF1 complementary DNA transfection. SF1 was essential for the induction of alternative splicing by the beta-catenin/TCF4 complex, and SF1 complementary DNA transfection induced known cancer-related splice variants, such as Wnt-induced secreted protein-1v and fibroblast growth factor receptor-3-ATII.


CONCLUSIONS
The beta-catenin/TCF4 complex regulates the level of SF1 protein expression, and, conversely, SF1 interacts with the complex and regulates its gene transactivation and premessenger RNA splicing activities. Identification of the interaction may shed light on a novel aspect of the Wnt signaling pathway.
Shitashige
Miki
M
Chemotherapy Division and Cancer Proteomics Project, National Cancer Center Research Institute, Tokyo, Japan.
Naishiro
Yasuyoshi
Y
Idogawa
Masashi
M
Honda
Kazufumi
K
Ono
Masaya
M
Hirohashi
Setsuo
S
Yamada
Tesshi
T
D000818:Animals; D001483:Base Sequence; D055511:CCN Intercellular Signaling Proteins; D019556:COS Cells; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D002522:Chlorocebus aethiops; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000096:biosynthesis; D040901:Proteomics / Q000379:methods; D011518:Proto-Oncogene Proteins; D012322:RNA Precursors / Q000378:metabolism*; D012326:RNA Splicing; D000072260:RNA Splicing Factors; D012333:RNA, Messenger / Q000378:metabolism*; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000096:biosynthesis; D015398:Signal Transduction; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D051153:Wnt Proteins / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
D055511:CCN Intercellular Signaling Proteins; C116396:CCN4 protein, human; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D012322:RNA Precursors; D000072260:RNA Splicing Factors; D012333:RNA, Messenger; C107467:SF1 protein, human; D051820:TCF Transcription Factors; C544894:TCF7L2 protein, human; C544895:Tcf7l2 protein, mouse; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D051153:Wnt Proteins; D051176:beta Catenin; C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3