Cellular Nucleic Acid Binding Protein Regulates the CT Element of the Human c- myc Protooncogene (*)

The CT element of the c- myc gene is required for promoter P1 usage and can drive expression of a heterologous promoter. Both double strand (Sp1) and single strand (hnRNP K) CT-binding proteins have been implicated as mediators of CT action. Although significant levels of CT activity persisted following Sp1 immunodepletion, EGTA totally abolished transactivation, thus implicating another metal requiring factor in CT element activity. As hnRNP K binds to one strand of the CT element, but has no metal requirement, the opposite (purine-rich strand) was examined as a target for a metal-dependent protein. A zinc-requiring purine strand binding activity was identified as cellular nucleic acid binding protein (CNBP), a protein previously implicated in the regulation of sterol responsive genes. Two forms of CNBP differed in their relative binding to the CT- or sterol-response elements. CNBP was shown to be a bona fide regulator of the CT element by cotransfection of a CNBP expression vector that stimulated expression of a CT-driven but not an AP1-dependent reporter. These data suggest that hnRNP K and CNBP bind to opposite strands and co-regulate the CT element.

[1]  N. Hay,et al.  Repeated CT elements bound by zinc finger proteins control the absolute and relative activities of the two principal human c-myc promoters , 1993, Molecular and cellular biology.

[2]  J. Sedivy,et al.  Effects of c-myc expression on proliferation, quiescence, and the G0 to G1 transition in nontransformed cells. , 1993, Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research.

[3]  S. J. Flint,et al.  Site-specific oligonucleotide binding represses transcription of the human c-myc gene in vitro. , 1988, Science.

[4]  B. Howard,et al.  Recombinant genomes which express chloramphenicol acetyltransferase in mammalian cells , 1982, Molecular and cellular biology.

[5]  D. Shalloway,et al.  An RNA-binding protein associated with Src through its SH2 and SH3 domains in mitosis , 1994, Nature.

[6]  X. Hua,et al.  SREBP-1, a membrane-bound transcription factor released by sterol-regulated proteolysis , 1994, Cell.

[7]  Gerard I. Evan,et al.  Induction of apoptosis in fibroblasts by c-myc protein , 1992, Cell.

[8]  A. Kimchi,et al.  Close link between reduction of c-myc expression by interferon and G0/G1 arrest , 1985, Nature.

[9]  M. Groudine,et al.  The block to transcriptional elongation within the human c-myc gene is determined in the promoter-proximal region. , 1992, Genes & development.

[10]  P. Leder,et al.  Cell-specific regulation of the c-myc gene by lymphocyte mitogens and platelet-derived growth factor , 1983, Cell.

[11]  T. Littlewood,et al.  Chromatin structure of transcriptionally active and inactive human c‐myc alleles. , 1985, The EMBO journal.

[12]  Brent H. Cochran,et al.  Molecular cloning of gene sequences regulated by platelet-derived growth factor , 1983, Cell.

[13]  H. Krutzsch,et al.  N-isopropyliodoacetamide in the reduction and alkylation of proteins: use in microsequence analysis. , 1993, Analytical biochemistry.

[14]  A. Firulli,et al.  Ribonucleoprotein and protein factors bind to an H-DNA-forming c-myc DNA element: possible regulators of the c-myc gene. , 1989, Proceedings of the National Academy of Sciences of the United States of America.

[15]  A. Patel,et al.  myc function and regulation. , 1992, Annual review of biochemistry.

[16]  M. Brown,et al.  SREBP-2, a second basic-helix-loop-helix-leucine zipper protein that stimulates transcription by binding to a sterol regulatory element. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[17]  R. Roeder,et al.  Eukaryotic gene transcription with purified components. , 1983, Methods in enzymology.

[18]  H. Lachman,et al.  Expression of c-myc changes during differentiation of mouse erythroleukaemia cells , 1984, Nature.

[19]  O. Hobert,et al.  Novel signaling pathway suggested by SH3 domain-mediated p95vav/heterogeneous ribonucleoprotein K interaction. , 1994, The Journal of biological chemistry.

[20]  G. Dreyfuss,et al.  Specific binding of heterogeneous ribonucleoprotein particle protein K to the human c-myc promoter, in vitro. , 1993, The Journal of biological chemistry.

[21]  D. Eick,et al.  Hold back of RNA polymerase II at the transcription start site mediates down‐regulation of c‐myc in vivo. , 1992, The EMBO journal.

[22]  K. Svenson,et al.  Identification of a zinc finger protein that binds to the sterol regulatory element. , 1989, Science.

[23]  G. Dreyfuss,et al.  Identification of Src, Fyn, and Lyn SH3-binding proteins: implications for a function of SH3 domains , 1994, Molecular and cellular biology.

[24]  G. Dreyfuss,et al.  Characterization and primary structure of the poly(C)-binding heterogeneous nuclear ribonucleoprotein complex K protein , 1992, Molecular and cellular biology.

[25]  P. Leder,et al.  Chromatin structure and protein binding in the putative regulatory region of the c-myc gene in burkitt lymphoma , 1984, Cell.

[26]  R. Weinberg,et al.  Multiple protein-binding sites in the 5'-flanking region regulate c-fos expression , 1986, Molecular and cellular biology.

[27]  G. Dreyfuss,et al.  The pre-mRNA binding K protein contains a novel evolutionarily conserved motif. , 1993, Nucleic acids research.

[28]  N. Hay,et al.  Regulatory elements that modulate expression of human c-myc. , 1987, Genes & development.