Regulation of monocyte chemoattractant protein (MCP)-1 transcription by interferon-gamma (IFN-gamma) in human astrocytoma cells: postinduction refractory state of the gene, governed by its upstream elements.
Monocyte chemoattractant protein (MCP)-1 is expressed by astrocytes in diverse inflammatory states and is a key regulator of monocyte recruitment to the central nervous system (CNS). In the current study, we addressed mechanisms by which transcription of the human MCP-1 gene (hMCP-1) was terminated, after induction by interferon (IFN)-gamma. Our results demonstrated that IFN-gamma-induced transcription of hMCP-1 was followed by a refractory state, during which hMCP-1 was resistant to restimulation by either IFN-gamma or heterologous activators such as TNF-alpha. This refractory state affected the hMCP-1 gene selectively, as other IFN-gamma-inducible genes remained responsive to restimulation. The IFN-gamma-induced hMCP-1 refractory state was governed at the transcriptional level and was sensitive to protein synthesis inhibitors, suggesting a requirement for newly expressed components. A minimal 213 base pair hMCP-1 regulatory element directed both IFN-gamma-mediated transcription and the subsequent refractory state. We previously demonstrated that IFN-gamma treatment resulted in coordinate protein occupancy in vivo of two hMCP-1 promoter elements, a gamma-activated site (GAS) and a GC-rich element. During the refractory state, IFN-gamma treatment failed to induce protection of either the hMCP-1 GAS element or the GC box. These results furnish insight into the expression of hMCP-1 during CNS inflammation and provide the first delineation of an IFN-gamma-induced transcriptional refractory state.
Zhou
Z H
ZH
Department of Neurosciences, The Lerner Research Institute, and The Mellen Center for Multiple Sclerosis Treatment and Research, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Han
Y
Y
Wei
T
T
Aras
S
S
Chaturvedi
P
P
Tyler
S
S
Rani
M R
MR
Ransohoff
R M
RM
D001254:Astrocytoma; D001483:Base Sequence; D018932:Chemokine CCL2 / Q000235:genetics*; D003513:Cycloheximide / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000502:physiology*; D005796:Genes; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007700:Kinetics; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D018932:Chemokine CCL2; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D003513:Cycloheximide