Transcriptional suppression of the human T-cell leukemia virus type I long terminal repeat occurs by an unconventional interaction of a CREB factor with the R region.
To analyze regulation of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR), cell lines were generated from LTR-tax x LTR-beta-galactosidase (beta-Gal) doubly transgenic mouse fibroblastic tumors. The HTLV-I LTR directs expression of both the tax and lacZ genes, and Tax up-modulates both promoters in primary cells. However, once cells were transformed by tax, beta-Gal but not tax expression was suppressed. Supertransformation of these cells with v-src suppressed both beta-Gal and tax expression. This suppression was reversed by treatment with the tyrosine kinase inhibitor herbimycin A or protein kinase A inhibitor H8. Electrophoretic mobility shift assays demonstrated augmented binding in the R but not U3 region. This binding was competitively inhibited by a high-affinity CREB oligodeoxynucleotide and super-shifted with a specific CREB antibody. Treatment of cells with the cyclic AMP analog dibutyryl cyclic AMP also transiently increased the R region binding dramatically. In vitro DNase I footprint analysis identified a protein-binding sequence in the R region which corresponded with suppression. However, this target sequence lacked a conventional CREB-binding site. A 70.5-kDa DNA-binding protein was partially purified by affinity chromatography, along with a 49-kDa protein which reacted with CREB-specific sera. These data demonstrate that HTLV-I LTR suppression is associated with CREB factor binding in the R region, probably by direct interaction with a 70.5-kDa protein, and provide a novel mechanism for maintenance of viral latency.
Xu
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Department of Neuropharmacology, Scripps Research Institute, La Jolla, California 92037.
Brown
D A
DA
Kitajima
I
I
Bilakovics
J
J
Fey
L W
LW
Nerenberg
M I
MI
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D016355:Genes, pX; D016391:Genes, src; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D014158:Transcription, Genetic
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D017868:Cyclic AMP-Dependent Protein Kinases