Translational control of MHC class II I-A molecules by IFN-gamma.
MHC class II molecules are expressed in a limited number of cell types, including B lymphocytes and macrophages (M phi). IFN-gamma increases the surface expression of class II molecules in a murine B cell line without inducing detectable changes in either I-A or I-A mRNA levels. In bone marrow-derived M phi, IFN-gamma causes an increase in class II expression at both the mRNA and surface levels. In addition to the increase in transcription rates described for M phi, IFN-gamma increases the rate of synthesis of IA alpha and IA beta proteins and the ribosome loading for both mRNA molecules in both cell types. Interestingly, there is a significant peak of free I-A mRNA in noninduced cells. Therefore, IFN-gamma regulates the expression of MHC class II molecules at the translational level in both B cells and M phi and, as already reported, at the transcriptional level only in M phi. The actual mechanism of regulation causes changes in the translation initiation rates in both cell types, as demonstrated by an increase in ribosome loading in polysome gradients.
Goñalons
E
E
Department de Fisiologia (Immunologia), Facultat de Biologia and Fundacio August Pi i Sunyer, Campus de Bellvitge, Universitat de Barcelona, Spain.
Barrachina
M
M
García-Sanz
J A
JA
Celada
A
A
D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D005802:Genes, MHC Class II / Q000187:drug effects / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics*; D007371:Interferon-gamma / Q000502:physiology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects / Q000276:immunology*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012260:Ribonucleases; D015534:Trans-Activators / Q000502:physiology; D014407:Tumor Cells, Cultured
D000949:Histocompatibility Antigens Class II; D012333:RNA, Messenger; D015534:Trans-Activators; D007371:Interferon-gamma; D012260:Ribonucleases