RESUMO
Growth-regulating cellular genes or genes encoding proteins involved in cell cycle control are likely to be major targets of viral gene products in the establishment of a cellular state favourable for a permissive infection. We have examined whether infection of permissive fibroblasts with human cytomegalovirus (HCMV) results in trans-regulation of such cellular genes. Here we have shown that the proto-oncogenes c-fos and c-myc are specifically induced during immediate early (IE) and early times of HCMV infection, as has recently been shown for the heat shock protein 70 gene (hsp70). Deletion analyses and transfection assays of all three promoters showed that previously defined control sequences upstream of the constitutive promoters and downstream of the mRNA cap site are not required for this up-regulation by HCMV, such that the minimal inducible promoters of c-fos, c-myc and the hsp70 gene contained only 50 to 60 bp upstream of the transcription start site. Cotransfection assays with vectors expressing HCMV major IE cDNAs showed that the 72K IE1 and 80K IE2 proteins are involved in the up-regulation of these promoters. IE1 and IE2 products independently were able to up-regulate the minimal constitutive promoters of the constructs tested here, but trans-activation by IE1 and IE2 together was synergistic. In the case of the hsp70 promoter, promoter constructs containing a variety of different TATA elements could be activated by the 72K IE1 and 80K IE2 proteins.
Assuntos
Citomegalovirus/metabolismo , Proteínas Imediatamente Precoces/metabolismo , Glicoproteínas de Membrana , Proteínas Nucleares/metabolismo , Regiões Promotoras Genéticas/genética , Transativadores/metabolismo , Proteínas do Envelope Viral , Proteínas Virais/metabolismo , Sequência de Bases , Citomegalovirus/genética , Análise Mutacional de DNA , Genes fos/genética , Genes myc/genética , Proteínas de Choque Térmico/genética , Humanos , Proteínas Imediatamente Precoces/genética , Dados de Sequência Molecular , Proteínas Nucleares/genética , RNA Mensageiro/metabolismo , Homologia de Sequência , TATA Box/genética , Transativadores/genética , Transcrição Gênica , Transfecção , Regulação para Cima , Proteínas Virais/genéticaRESUMO
We studied the effects of adding cytomegalovirus (CMV) in vitro to normal human bone marrow mononuclear cells (BM-MNCs), committed myeloid progenitor cells, primitive myeloid blast-colony forming cells, and pre-formed marrow stromal cell monolayers in order to shed light on the mechanism by which hemopoiesis is suppressed in patients who acquire systemic CMV infection after allogeneic bone marrow transplantation. Incubation of BM-MNCs or committed progenitor cells with laboratory strain AD169 or wild strain CMV had no significant effect on total colony numbers or the morphology of component cells. CMV mRNA was not identified by in situ hybridization. In contrast, incubating marrow stromal monolayers with CMV produced specific cytopathic effects in fibroblasts and adipocytes and reduced the capacity of the stromal layers to support the proliferation of primitive myeloid progenitor cells. We conclude that CMV infection may impair hemopoiesis in vivo by a direct effect on the cellular components of the marrow stroma.
