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Stimulation of HLA-A Gene Expression through CRM-1-Dependent Nuclear RNA Export1

,
,¶
* Massey Cancer Center, Virginia Commonwealth University Medical Center, Richmond, VA 23298; and
Department of Biochemistry,
Department of Internal Medicine,
Department of Microbiology and Immunology, and
¶ Department of Human Genetics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298
IFNs regulate most MHC class I genes by stimulating transcription initiation. As shown previously, IFN-
controls HLA-A expression primarily at the posttranscriptional level. We have defined two 8-base sequences in a 39-nucleotide region in the 3'-transcribed region of the HLA-A gene that are required for the posttranscriptional response to IFN-
. Stimulation of HLA-A expression by IFN-
requires nuclear export of HLA-A mRNA by chromosome maintenance region 1 (CRM-1). Treatment of cells with leptomycin B, a specific inhibitor of CRM-1, completely inhibited IFN-
induction of HLA-A. Expression of a truncated, dominant-negative form of the nucleoporin NUP214/CAN,
CAN, that specifically interacts with CRM-1, also prevented IFN-
stimulation of HLA-A, providing confirmation of the role of CRM-1. Increased expression of HLA-A induced by IFN-
also requires protein methylation, as shown by the fact that treatment of SK-N-MC cells or HeLa cells with the PRMT1 inhibitor 5'-methyl-5'-thioadenosine abolished the cellular response to IFN-
. In contrast with HLA-A, IFN-
-induced expression of the HLA class Ib gene, HLA-E, was not affected by either 5'-methyl-5'-thioadenosine or leptomycin B. These results provide proof of principle that it is possible to differentially modulate the IFN-
-induced expression of the HLA-E and HLA-A genes, whose products often mediate opposing effects on cellular immunity to tumor cells, pathogens, and autoantigens.
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1 This work was supported by National Cancer Institute Grant CA87496 (to G.D.G.) and by the Massey Cancer Center, Virginia Commonwealth University.
2 Current address: Department of Medicine, Brigham and Womens Hospital, Boston, MA 02115.
3 Address correspondence and reprint requests to Dr. Gordon D. Ginder, Massey Cancer Center, 401 College Street, P.O. Box 980037, Richmond, VA 23298-0037. E-mail address: gdginder{at}vcu.edu
4 Abbreviations used in this paper: MHC-I, MHC class I; MHC-Ia, MHC-I class Ia; ISRE, IFN-stimulated response element; IRF-1, IFN regulatory factor 1; IRR, IFN response region; UIRR, upstream IRR; nt, nucleotide; LMB, leptomycin B; CRM-1, chromosome maintenance region 1; MTA, 5'-methyl-5'-thioadenosine; Tta, Tet transactivator protein; NES, nuclear export sequence; hnRNPA1, heteronuclear ribonucleoprotein A1.
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