Human cytomegalovirus product UL44 downregulates the transactivation of HIV-1 long terminal repeat.
OBJECTIVE
Human cytomegalovirus (HCMV) is often isolated from HIV-1-infected patients and the two viruses can infect the same cell type giving rise to direct bidirectional interactions. Whereas the long terminal repeat (LTR) transactivation ability of HCMV immediate early gene (IE1/IE2) is well documented, no information is available on the possible role of other HCMV proteins. In this study, the activity of ppUL44, an early DNA-binding protein, on HIV LTR transactivation was investigated.


METHODS
HIV LTR transactivation by ppUL44 in presence or absence of HIV-1 Tat and HCMV IE1/IE2 was determined in J-Jhan and U973 cells through transient transfection experiments with a series of different expression vectors. Some experiments were also performed on U373-MG astrocytoma cells permanently transfected with UL44 or with another HCMV gene used as a control (UL55).


RESULTS
The basal transactivation activity of the HIV LTR was not influenced by the presence of ppUL44. On the contrary, the transactivation observed in the presence of Tat, IE1/IE2 or both factors in synergy was strongly downregulated by ppUL44 in a dose-dependent manner. Deletion constructs of ppUL44 demonstrated that the region of the molecule responsible for the inhibition of the LTR is located within the last 114 amino acids at the carboxyl-terminal region.


CONCLUSIONS
The results obtained indicate that within the last 114 amino acids of ppUL44 there is a domain that has a negative effect on the ability of HIV-1 LTR to be activated by both its autologous transactivator Tat and the heterologous transactivator HCMV IE1/IE2 functioning individually or synergistically.
Boccuni
M C
MC
Department of Clinical and Experimental Medicine, University of Bologna, Italy.
Campanini
F
F
Battista
M C
MC
Bergamini
G
G
Dal Monte
P
P
Ripalti
A
A
Landini
M P
MP
D001254:Astrocytoma; D003587:Cytomegalovirus / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D015536:Down-Regulation; D005455:Fluorescent Antibody Technique; D015756:Genes, tat; D005822:Genetic Vectors; D016325:HIV Long Terminal Repeat / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics; D008156:Luciferases / Q000032:analysis; D008562:Membrane Glycoproteins; D016366:Open Reading Frames; D010957:Plasmids; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014759:Viral Envelope Proteins; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology
D004268:DNA-Binding Proteins; C072217:ICP36 protein, Cytomegalovirus; C069186:IE2 protein, Cytomegalovirus; D017874:Immediate-Early Proteins; D008562:Membrane Glycoproteins; D015534:Trans-Activators; C077406:UL115 protein, Human herpesvirus 5; D014759:Viral Envelope Proteins; D014764:Viral Proteins; C071440:glycoprotein H, Cytomegalovirus; C499358:glycoprotein H, Human cytomegalovirus; C439068:glycoprotein O, cytomegalovirus; D008156:Luciferases