The human cytomegalovirus (HCMV) UL36–38 immediate-early (IE) locus encodes the UL37 exon 1 (pUL37x1) and UL37 (gpUL37) regulatory proteins, which have anti-apoptotic activities. pUL37x1 shares its entire sequence, including a hydrophobic leader and an acidic domain, with the exception of one residue, with the amino terminus of gpUL37. gpUL37 has, in addition, unique -linked glycosylation, transmembrane and cytosolic domains. A rabbit polyvalent antiserum was generated against residues 27–40 in the shared amino-terminal domain and a mouse polyvalent antiserum was generated against the full-length protein to study trafficking of individual UL37 proteins in human cells that transiently expressed gpUL37 or pUL37x1. Co-localization studies by confocal laser scanning microscopy detected trafficking of gpUL37 and pUL37x1 from the endoplasmic reticulum to the Golgi apparatus in permissive U373 cells and in human diploid fibroblasts (HFF). Trafficking of gpUL37 to the cellular plasma membrane was detected in unfixed HFF cells. FLAG-tagged gpUL37 trafficked similarly through the secretory apparatus to the plasma membrane. By using confocal microscopy and immunoblotting of fractionated cells, gpUL37 and pUL37x1 were found to co-localize with mitochondria in human cells. This unconventional dual trafficking pattern through the secretory apparatus and to mitochondria is novel for herpesvirus IE regulatory proteins.


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  1. Al-Barazi, H. O. & Colberg-Poley, A. M. (1996). The human cytomegalovirus UL37 immediate-early regulatory protein is an integral membrane N-glycoprotein which traffics through the endoplasmic reticulum and Golgi apparatus.Journal of Virology 70, 7198-7208. [Google Scholar]
  2. Ardail, D., Gasnier, F., Lermé, F., Simonot, C., Louisot, P. & Gateau-Roesch, O. (1993). Involvement of mitochondrial contact sites in the subcellular compartmentalization of phospholipid biosynthetic enzymes.Journal of Biological Chemistry 268, 25985-25992. [Google Scholar]
  3. Biegalke, B. J. (1999). Human cytomegalovirus US3 gene expression is regulated by a complex network of positive and negative regulators.Virology 261, 155-164.[CrossRef] [Google Scholar]
  4. 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]
  5. Chomyn, A. (1996). In vivo labeling and analysis of human mitochondrial translation products.Methods in Enzymology 264, 197-211. [Google Scholar]
  6. Colberg-Poley, A. M., Santomenna, L. D., Harlow, P. P., Benfield, P. A. & Tenney, D. J. (1992). Human cytomegalovirus US3 and UL36–38 immediate-early proteins regulate gene expression.Journal of Virology 66, 95-105. [Google Scholar]
  7. Colberg-Poley, A. M., Huang, L., Soltero, V. E., Iskenderian, A. C., Schumacher, R.-F. & Anders, D. G. (1998). The acidic domain of pUL37x1 and gpUL37 plays a key role in transactivation of HCMV DNA replication gene promoter constructions.Virology 246, 400-408.[CrossRef] [Google Scholar]
  8. Colberg-Poley, A. M., Soltero, V. E. & Schumacher, R. F. (2000). Analysis of cytomegalovirus gene expression by transfection.Methods in Molecular Medicine 33, 67-77. [Google Scholar]
  9. Fish, K. N., Söderberg-Nauclér, C. & Nelson, J. A. (1998). Steady-state plasma membrane expression of human cytomegalovirus gB is determined by the phosphorylation state of Ser900.Journal of Virology 72, 6657-6664. [Google Scholar]
  10. Goldmacher, V. S., Bartle, L. M., Skaletskaya, A., Dionne, C. A., Kedersha, N. L., Vater, C. A., Han, J.-W., Lutz, R. J., Watanabe, S., McFarland, E. D. C., Kieff, E. D., Mocarski, E. S. & Chittenden, T. (1999). A cytomegalovirus-encoded mitochondria-localized inhibitor of apoptosis structurally unrelated to Bcl-2.Proceedings of the National Academy of Sciences, USA 96, 12536-12541.[CrossRef] [Google Scholar]
  11. Hagemeier, C., Walker, S., Caswell, R., Kouzarides, T. & Sinclair, J. (1992). 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]
  12. Hillson, D. A., Lambert, N. & Freedman, R. B. (1984). Formation and isomerization of disulfide bonds in proteins: protein disulfide-isomerase.Methods in Enzymology 107, 281-294. [Google Scholar]
  13. Kouzarides, T., Bankier, A. T., Satchwell, S. C., Preddy, E. & Barrell, B. G. (1988). An immediate early gene of human cytomegalovirus encodes a potential membrane glycoprotein.Virology 165, 151-164.[CrossRef] [Google Scholar]
  14. 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]
  15. Ni, L., Heard, T. S. & Weiner, H. (1999).In vivo mitochondrial import. A comparison of leader sequence charge and structural relationships with the in vitro model resulting in evidence for co-translational import.Journal of Biological Chemistry 274, 12685-12691.[CrossRef] [Google Scholar]
  16. Paddock, S. W. (1999). An introduction to confocal imaging.Methods in Molecular Biology 122, 1-34. [Google Scholar]
  17. Pari, G. S. & Anders, D. G. (1993). Eleven loci encoding trans-acting factors are required for transient complementation of human cytomegalovirus oriLyt-dependent DNA replication.Journal of Virology 67, 6979-6988. [Google Scholar]
  18. Pari, G. S., Kacica, M. A. & Anders, D. G. (1993). Open reading frames UL44, IRS1/TRS1, and UL36–38 are required for transient complementation of human cytomegalovirus oriLyt-dependent DNA synthesis.Journal of Virology 67, 2575-2582. [Google Scholar]
  19. Rusiñol, A. E., Cui, Z., Chen, M. H. & Vance, J. E. (1994). A unique mitochondria-associated membrane fraction from rat liver has a high capacity for lipid synthesis and contains pre-Golgi secretory proteins including nascent lipoproteins.Journal of Biological Chemistry 269, 27494-27502. [Google Scholar]
  20. Sambucetti, L. C., Cherrington, J. M., Wilkinson, G. W. G. & Mocarski, E. S. (1989). NF-kappa B activation of the cytomegalovirus enhancer is mediated by a viral transactivator and by T cell stimulation.EMBO Journal 8, 4251-4258. [Google Scholar]
  21. Tenney, D. J. & Colberg-Poley, A. M. (1991a). Expression of the human cytomegalovirus UL36–38 immediate early region during permissive infection.Virology 182, 199-210.[CrossRef] [Google Scholar]
  22. Tenney, D. J. & Colberg-Poley, A. M. (1991b). Human cytomegalovirus UL36–38 and US3 immediate-early genes: temporally regulated expression of nuclear, cytoplasmic, and polysome-associated transcripts during infection.Journal of Virology 65, 6724-6734. [Google Scholar]
  23. Tenney, D. J., Santomenna, L. D., Goudie, K. B. & Colberg-Poley, A. M. (1993). The human cytomegalovirus US3 immediate-early protein lacking the putative transmembrane domain regulates gene expression.Nucleic Acids Research 21, 2931-2937.[CrossRef] [Google Scholar]
  24. von Heijne, G. (1986). Mitochondrial targeting sequences may form amphiphilic helices.EMBO Journal 5, 1335-1342. [Google Scholar]
  25. Walter, P. & Johnson, A. E. (1994). Signal sequence recognition and protein targeting to the endoplasmic reticulum membrane.Annual Review of Cell Biology 10, 87-119.[CrossRef] [Google Scholar]
  26. Zhang, H., Al-Barazi, H. O. & Colberg-Poley, A. M. (1996). The acidic domain of the human cytomegalovirus UL37 immediate early glycoprotein is dispensable for its transactivating activity and localization but is not for its synergism.Virology 223, 292-302.[CrossRef] [Google Scholar]

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