The IE2 protein of human cytomegalovirus transactivates viral and cellular promoters through a wide variety of -elements, but the mechanism of its action has not been well characterized. Here, IE2–Sp1 synergy and IE2–TATA box-binding protein (TBP) interaction are examined by artificial recruitment of either Sp1 or TBP to the promoter. It was found that IE2 could cooperate with DNA-bound Sp1. A 117 amino acid glutamine-rich fragment of Sp1, which can interact with TAF110 and human TAF130, was sufficient for the augmentation of IE2-driven transactivation. In binding assays , IE2 interacted directly with the C-terminal region of Sp1, which contains the zinc finger DNA-binding domain, but not with its transactivation domain, suggesting that synergy between IE2 and the transactivation domain of Sp1 might be mediated by other proteins such as TAF or TBP. It was also found that TBP recruitment to the promoter markedly increased IE2-mediated transactivation. Thus, IE2 acts synergistically with DNA-bound Sp1 and DNA-bound TBP. These results suggest that, in human cytomegalovirus IE2 transactivation, Sp1 functions at an early step such as recruitment of TBP and IE2 acts to accelerate rate-limiting steps after TBP recruitment.


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  1. Arlt, H., Lang, D., Gebert, S. & Stamminger, T. (1994). Identification of binding sites for the 86-kilodalton IE2 protein of human cytomegalovirus within an IE2-responsive viral early promoter. Journal of Virology 68, 4117-4125. [Google Scholar]
  2. Biegalke, B. J. & Geballe, A. P. (1991). Sequence requirements for activation of the HIV-1 LTR by human cytomegalovirus. Virology 183, 381-385.[CrossRef] [Google Scholar]
  3. Blau, J., Xiao, H., McCracken, S., O’Hare, P., Greenblatt, J. & Bentley, D. (1996). Three functional classes of transcriptional activation domain. Molecular and Cellular Biology 16, 2044-2055. [Google Scholar]
  4. Buratowski, S., Hahn, S., Guarente, L. & Sharp, P. A. (1989). Five intermediate complexes in transcription initiation by RNA polymerase II. Cell 56, 549-561.[CrossRef] [Google Scholar]
  5. Caswell, R., Hagemeier, C., Chiou, C.-J., Hayward, G., Kouzarides, T. & Sinclair, J. (1993). The human cytomegalovirus 86K immediate early (IE) 2 protein requires the basic region of the TATA-box binding protein (TBP) for binding, and interacts with TBP and transcription factor TFIIB via regions of IE2 required for transcriptional regulation. Journal of General Virology 74, 2691-2698.[CrossRef] [Google Scholar]
  6. Chatterjee, S. & Struhl, K. (1995). Connecting a promoter-bound protein to TBP bypasses the need for a transcriptional activation domain. Nature 374, 820-822.[CrossRef] [Google Scholar]
  7. Chen, J. L., Attardi, L. D., Verrijzer, C. P., Yokomori, K. & Tjian, R. (1994). Assembly of recombinant TFIID reveals differential coactivator requirements for distinct transcriptional activators. Cell 79, 93-105.[CrossRef] [Google Scholar]
  8. Choi, K. S., Kim, S.-J. & Kim, S. (1995). The retinoblastoma gene product negatively regulates transcriptional activation mediated by the human cytomegalovirus IE2 protein. Virology 208, 450-456.[CrossRef] [Google Scholar]
  9. Chun, R. F. & Jeang, K. T. (1996). Requirements for RNA polymerase II carboxyl-terminal domain for activated transcription of human retroviruses human T-cell lymphotropic virus I and HIV-1. Journal of Biological Chemistry 271, 27888-27894.[CrossRef] [Google Scholar]
  10. Chun, R. F., Semmes, O. J., Neuveut, C. & Jeang, K. T. (1998). Modulation of Sp1 phosphorylation by human immunodeficiency virus type 1 Tat. Journal of Virology 72, 2615-2629. [Google Scholar]
  11. Courey, A. J. & Tjian, R. (1988). Analysis of Sp1 in vivo reveals multiple transcriptional domains, including a novel glutamine-rich activation motif. Cell 55, 887-898.[CrossRef] [Google Scholar]
  12. Dynan, W. S. & Tjian, R. (1983a). Isolation of transcription factors that discriminate between different promoters recognized by RNA polymerase II. Cell 32, 669-680.[CrossRef] [Google Scholar]
  13. Dynan, W. S. & Tjian, R. (1983b). The promoter-specific transcription factor Sp1 binds to upstream sequences in the SV40 early promoter. Cell 35, 79-87.[CrossRef] [Google Scholar]
  14. Emami, K. H., Navarre, W. W. & Smale, S. T. (1995). Core promoter specificities of the Sp1 and VP16 transcriptional activation domains. Molecular and Cellular Biology 15, 5906-5916. [Google Scholar]
  15. Emili, A., Greenblatt, J. & Ingles, C. J. (1994). Species-specific interaction of the glutamine-rich activation domains of Sp1 with the TATA box-binding protein. Molecular and Cellular Biology 14, 1582-1593. [Google Scholar]
  16. Everett, R. D., Baty, D. & Chambon, P. (1983). The repeated GC-rich motifs upstream from the TATA box are important elements of the SV40 early promoter. Nucleic Acids Research 11, 2447-2464.[CrossRef] [Google Scholar]
  17. Gill, G., Pascal, E., Tseng, Z. H. & Tjian, R. (1994). A glutamine-rich hydrophobic patch in transcription factor Sp1 contacts the dTAFII110 component of the Drosophila TFIID complex and mediates transcriptional activation. Proceedings of the National Academy of Sciences, USA 91, 192-196.[CrossRef] [Google Scholar]
  18. Hagemeier, C., Walker, S., Caswell, R., Kouzarides, T. & Sinclair, J. (1992a). The human cytomegalovirus 80-kilodalton but not the 72-kilodalton immediate-early protein transactivates heterologous promoters in a TATA box-dependent mechanism and interacts directly with TFIID. Journal of Virology 66, 4452-4456. [Google Scholar]
  19. Hagemeier, C., Walker, S. M., Sissons, P. J. G. & Sinclair, J. H. (1992b). The 72K IE1 and 80K IE2 proteins of human cytomegalovirus independently trans-activate the c-fos, c-myc and hsp70 promoters via basal promoter elements. Journal of General Virology 73, 2385-2393.[CrossRef] [Google Scholar]
  20. Hermiston, T. W., Malone, C. L., Witte, P. R. & Stinski, M. F. (1987). Identification and characterization of the human cytomegalovirus immediate-early region 2 gene that stimulates gene expression from an inducible promoter. Journal of Virology 61, 3214-3221. [Google Scholar]
  21. Jeang, K. T., Chun, R., Lin, N. H., Gatignol, A., Glabe, C. G. & Fan, H. (1993). In vitro and in vivo binding of human immunodeficiency virus type 1 Tat protein and Sp1 transcription factor. Journal of Virology 67, 6224-6233. [Google Scholar]
  22. Jones, K. A., Kadonaga, J. T., Luciw, P. A. & Tjian, R. (1986). Activation of the AIDS retrovirus promoter by the cellular transcription factor, Sp1. Science 232, 755-759.[CrossRef] [Google Scholar]
  23. Jupp, R., Hoffmann, S., Stenberg, R. M., Nelson, J. A. & Ghazal, P. (1993). Human cytomegalovirus IE86 protein interacts with promoter-bound TATA-binding protein via a specific region distinct from the autorepression domain. Journal of Virology 67, 7539-7546. [Google Scholar]
  24. Kadonaga, J. T., Carner, K. R., Masiarz, F. R. & Tjian, R. (1987). Isolation of cDNA encoding transcription factor Sp1 and functional analysis of the DNA binding domain. Cell 51, 1079-1090.[CrossRef] [Google Scholar]
  25. Kaufmann, J. & Smale, S. T. (1994). Direct recognition of initiator elements by a component of the transcription factor IID complex. Genes & Development 8, 821-829.[CrossRef] [Google Scholar]
  26. Kim, S., Yu, S. S. & Kim, V. N. (1996). Essential role of NF-κB in transactivation of the human immunodeficiency virus long terminal repeat by the human cytomegalovirus IE1 protein. Journal of General Virology 77, 83-91.[CrossRef] [Google Scholar]
  27. Kim, J.-M., Hong, Y., Kim, S., Cho, M. H., Yoshida, M., Jeang, K. T., Burns, W. & Kim, S. (1999). Sequences downstream of the RNA initiation site of the HTLV type I long terminal repeat are sufficient for trans-activation by human cytomegalovirus immediate-early proteins. AIDS Research and Human Retroviruses 15, 545-550.[CrossRef] [Google Scholar]
  28. Kobayashi, N., Boyer, T. G. & Berk, A. J. (1995). A class of activation domains interacts directly with TFIIA and stimulates TFIIA–TFIID–promoter complex assembly. Molecular and Cellular Biology 15, 6465-6473. [Google Scholar]
  29. Koleske, A. J. & Young, R. A. (1994). An RNA polymerase II holoenzyme responsive to activators. Nature 368, 466-469.[CrossRef] [Google Scholar]
  30. Lee, J. S., Galvin, K. M. & Shi, Y. (1993). Evidence for physical interaction between the zinc-finger transcription factors YY1 and Sp1. Proceedings of the National Academy of Sciences, USA 90, 6145-6149.[CrossRef] [Google Scholar]
  31. Lee, J. S., Galvin, K. M., See, R. H., Eckner, R., Livingston, D., Moran, E. & Shi, Y. (1995). Relief of YY1 transcriptional repression by adenovirus E1A is mediated by E1A-associated protein p300. Genes & Development 9, 1188-1198.[CrossRef] [Google Scholar]
  32. Lin, Y.-S., Ha, I., Maldonado, E., Reinberg, D. & Green, M. R. (1991). Binding of general transcription factor TFIIB to an acidic activating region. Nature 353, 569-571.[CrossRef] [Google Scholar]
  33. Lukac, D. M., Manuppello, J. R. & Alwine, J. C. (1994). Transcriptional activation by the human cytomegalovirus immediate-early proteins: requirements for simple promoter structures and interactions with multiple components of the transcription complex. Journal of Virology 68, 5184-5193. [Google Scholar]
  34. Lukac, D. M., Harel, N. Y., Tanese, N. & Alwine, J. C. (1997). TAF-like functions of human cytomegalovirus immediate-early proteins. Journal of Virology 71, 7227-7239. [Google Scholar]
  35. Malone, C. L., Vesole, D. H. & Stinski, M. F. (1990). Transactivation of a human cytomegalovirus early promoter by gene products from the immediate-early gene IE2 and augmentation by IE1: mutational analysis of the viral proteins. Journal of Virology 64, 1498-1506. [Google Scholar]
  36. Mocarski, E. S.Jr (1996). Cytomegaloviruses and their replication. In Fields Virology, pp. 2447-2492. Edited by B. N. Fields, D. M. Knipe & P. M. Howley. Philadelphia: Lippincott–Raven.
  37. Nabel, G. & Baltimore, D. (1987). An inducible transcription factor activates expression of human immunodeficiency virus in T cells. Nature 326, 711-713.[CrossRef] [Google Scholar]
  38. Pizzorno, M. C. & Hayward, G. S. (1990). The IE2 gene products of human cytomegalovirus specifically down-regulate expression from the major immediate-early promoter through a target sequence located near the cap site. Journal of Virology 64, 6154-6165. [Google Scholar]
  39. Ptashne, M. & Gann, A. (1997). Transcriptional activation by recruitment. Nature 386, 569-577.[CrossRef] [Google Scholar]
  40. Saluja, D., Vassallo, M. F. & Tanese, N. (1998). Distinct subdomains of human TAFII130 are required for interactions with glutamine-rich transcriptional activators. Molecular and Cellular Biology 18, 5734-5743. [Google Scholar]
  41. Schwartz, R., Helmich, B. & Spector, D. H. (1996). CREB and CREB-binding proteins play an important role in the IE2 86-kilodalton protein-mediated transactivation of the human cytomegalovirus 2·2-kilobase RNA promoter. Journal of Virology 70, 6955-6966. [Google Scholar]
  42. Seipel, K., Georgiev, O., Gerber, H. P. & Schaffner, W. (1993). C-terminal domain (CTD) of RNA polymerase II and N-terminal segment of the human TATA binding protein (TBP) can mediate remote and proximal transcriptional activation, respectively. Nucleic Acids Research 21, 5609-5615.[CrossRef] [Google Scholar]
  43. Stargell, L. A. & Struhl, K. (1996). Mechanisms of transcriptional activation in vivo: two steps forward. Trends in Genetics 12, 311-315.[CrossRef] [Google Scholar]
  44. Stringer, K. F., Ingles, C. J. & Greenblatt, J. (1990). Direct and selective binding of an acidic transcriptional activation domain to the TATA-box factor TFIID. Nature 345, 783-786.[CrossRef] [Google Scholar]
  45. Strubin, M. & Struhl, K. (1992). Yeast and human TFIID with altered DNA-binding specificity for TATA elements. Cell 68, 721-730.[CrossRef] [Google Scholar]
  46. Struhl, K. (1996). Chromatin structure and RNA polymerase II connection: implications for transcription. Cell 84, 179-182.[CrossRef] [Google Scholar]
  47. Tansey, W. P., Ruppert, S., Tjian, R. & Herr, W. (1994). Multiple regions of TBP participate in the response to transcriptional activators in vivo. Genes & Development 8, 2756-2769.[CrossRef] [Google Scholar]
  48. Tjian, R. & Maniatis, T. (1994). Transcriptional activation: a complex puzzle with few easy pieces. Cell 77, 5-8.[CrossRef] [Google Scholar]
  49. Wu, J., O’Neill, J. & Barbosa, M. S. (1998). Transcription factor Sp1 mediates cell-specific trans-activation of the human cytomegalovirus DNA polymerase gene promoter by immediate-early protein IE86 in glioblastoma U373MG cells. Journal of Virology 72, 236-244. [Google Scholar]
  50. Xiao, H., Friesen, J. D. & Lis, J. T. (1995). Recruiting TATA-binding protein to a promoter: transcriptional activation without an upstream activator. Molecular and Cellular Biology 15, 5757-5761. [Google Scholar]
  51. Xiao, H., Lis, J. T. & Jeang, K. T. (1997). Promoter activity of Tat at steps subsequent to TATA-binding protein recruitment. Molecular and Cellular Biology 17, 6898-6905. [Google Scholar]
  52. Yoo, Y. D., Chiou, C.-J., Choi, K. S., Yi, Y., Michelson, S., Kim, S., Hayward, G. S. & Kim, S.-J. (1996). The IE2 regulatory protein of human cytomegalovirus induces expression of the human transforming growth factor β1 gene through an Egr-1 binding site. Journal of Virology 70, 7062-7070. [Google Scholar]
  53. Yurochko, A. D., Mayo, M. W., Poma, E. E., Baldwin, A. S.Jr & Huang, E.-S. (1997). Induction of the transcription factor Sp1 during human cytomegalovirus infection mediates upregulation of the p65 and p105/p50 NF-κB promoters. Journal of Virology 71, 4638-4648. [Google Scholar]
  54. Zawel, L. & Reinberg, D. (1993). Initiation of transcription by RNA polymerase II: a multi-step process. Progress in Nucleic Acid Research and Molecular Biology 44, 67-108. [Google Scholar]
  55. Zhou, Q., Gedrich, R. W. & Engel, D. A. (1995). Transcriptional repression of the c-fos gene by YY1 is mediated by a direct interaction with ATF/CREB. Journal of Virology 69, 4323-4330. [Google Scholar]

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