title: bHLH-zip transcription factor Spz1 mediates mitogen-activated protein kinase cell proliferation, transformation, and tumorigenesis.
abstract: BHLH-zip proteins usually play important regulatory roles in cell growth and differentiation. In this study, we show that Spz1, a bHLH-zip transcription factor, acts downstream of mitogen-activated protein kinase (MAPK, extracellular signal-regulated kinase 1/2) to up-regulate cell proliferation and tumorigenesis. In addition, through an interaction with proliferating cell nuclear antigen (PCNA) promoter, Spz1 induced cell proliferation concomitant with an increase in PCNA gene expression. Spz1-transfected cells formed colony foci on soft agar and developed fibrosarcoma tumors in nude mice. MAPK directly interacted and phosphorylated Spz1 protein, which increased PCNA transcription and cell tumorigenic activities. Reduction of endogenous Spz1 expression via RNA interference decreased cell proliferation in p19 embryonic carcinoma cells. High levels of Spz1 expression were detected in murine tumor cell lines and tumor samples of both human and Spz1 transgenic mice. Thus, Spz1 may act as a proto-oncogene, participating in the MAPK signal pathway, and be a potential therapeutic target in the treatment of Ras-induced tumors.
authors.affiliation: Institute of Molecular Biology, Academia Sinica.
authors.forename: Shih-Hsien
authors.initials: SH
authors.lastname: Hsu
authors.forename: Hsiu-Mei
authors.initials: HM
authors.lastname: Hsieh-Li
authors.forename: Hsin-Yi
authors.initials: HY
authors.lastname: Huang
authors.forename: Pei-Hsin
authors.initials: PH
authors.lastname: Huang
authors.forename: Hung
authors.initials: H
authors.lastname: Li
mesh_terms: D000818:Animals; D041702:BALB 3T3 Cells; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism; D019556:COS Cells; D002453:Cell Cycle / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D018809:Proliferating Cell Nuclear Antigen / Q000096:biosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D015854:Up-Regulation
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D020928:Mitogen-Activated Protein Kinases; D018809:Proliferating Cell Nuclear Antigen; D000090063:Proto-Oncogene Mas; D014157:Transcription Factors; C000715470:MAS1 protein, human; C426848:Spz1 protein, mouse