Enhanced B7-2 gene expression by interferon-gamma in human monocytic cells is controlled through transcriptional and posttranscriptional mechanisms.
B7-2 is a costimulatory molecule expressed on professional antigen-presenting cells that provides T cells with a critical signal resulting in T-cell activation. Interferon-gamma (IFN-gamma) enhances B7-2 protein expression in monocytic cells. However, the molecular mechanisms controlling the enhanced expression of B7-2 are poorly understood. Northern blot and flow cytometry analysis revealed that human monocytes and the human monocytic cell line MonoMac6 (MM6) constitutively expressed B7-2 mRNA and protein and IFN-gamma treatment further enhanced the expression of both molecules. The ability of IFN-gamma to enhance B7-2 mRNA was evident at the dose of 31 U/mL and reached plateau levels at 500 U/mL. The effects of IFN-gamma on B7-2 mRNA expression were time dependent and occurred within 3 hours of treatment and increased through 24 hours. In vitro transcription assays and mRNA stability experiments showed that IFN-gamma increases both transcriptional activity and the stability of B7-2 mRNA. Treatment of MM6 cells with cycloheximide showed that de novo protein synthesis was not required for the IFN-gamma-enhanced expression of B7-2 mRNA. Overall, these studies show for the first time that IFN-gamma-enhanced expression of B7-2 protein in human monocytic cells is controlled at the gene level through a dual mechanism involving transcriptional and posttranscriptional mechanisms.
Curiel
R E
RE
Department of Medicine and Stanley S. Scott Cancer Center, Louisiana State University Medical Center, New Orleans, LA, USA.
Garcia
C S
CS
Rottschafer
S
S
Bosco
M C
MC
Espinoza-Delgado
I
I
D015703:Antigens, CD / Q000096:biosynthesis* / Q000235:genetics; D000998:Antiviral Agents / Q000494:pharmacology*; D051940:B7-2 Antigen; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D009000:Monocytes / Q000502:physiology*; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D014158:Transcription, Genetic
D015703:Antigens, CD; D000998:Antiviral Agents; D051940:B7-2 Antigen; C497964:CD86 protein, human; D008562:Membrane Glycoproteins; D007371:Interferon-gamma