The Epstein-Barr virus (EBV) ORI1yt enhancer is not B-cell specific and does not respond synergistically to the EBV transcription factors R and Z.
The Epstein-Barr virus DR promoter is located upstream of the PstI repeats, and in addition to the TATA box, it contains an upstream region (positions -69 to -220) responsive to EB1 (Z) (the BZLF1-encoded transcription factor) and an enhancer with two functionally distinct domains, A and B. Domain B has been described as a B-cell-specific EB1-responsive element (P. M. Lieberman, J. M. Hardwick, and S. D. Hayward, J. Virol. 63:3040-3050, 1989) activated synergistically by EB1 and R, an EBV early product encoded by the open reading frame BRLF1 (M. A. Cox, J. Leahy, and J. M. Hardwick, J. Virol. 64:313-321, 1990). We show here that domain B is an R-responsive element in HeLa cells and is therefore not an EB1-responsive B-cell-specific element. However, there is an EB1-binding site (ZRE-B) located within the R-responsive enhancer region. ZRE-B can be deleted without affecting the R-dependent enhancer activity. Moreover, there is no cooperation or synergy between R and EB1 when activating the B domain (ZRE-B plus the R-responsive element) positioned as an enhancer. ZRE-B is therefore not part of the R-inducible enhancer. We have tested several subregions of the DR enhancer B domain, either alone or in combination, for their capacity to transmit the R-activating signal to the rabbit beta-globin promoter. We found that the R-responsive element is composed of four protoenhancers that span the whole B domain. These protoenhancers alone are weakly or not responsive to R. One of the protoenhancers contains the overlapping palindromes 5'-TTGTCCcgtGGACAAaTGTCC-3'. However, one palindrome, either alone or duplicated, or the overlapping palindromes did not respond to R.
Gruffat
H
H
Laboratoire de Virologie Moléculaire, Ecole Normale Supérieure de Lyon, France.
Moreno
N
N
Sergeant
A
A
D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D003001:Cloning, Molecular; D015342:DNA Probes; D004279:DNA, Viral / Q000235:genetics; D004742:Enhancer Elements, Genetic; D004926:Escherichia coli / Q000235:genetics; D005914:Globins / Q000235:genetics; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D015183:Restriction Mapping; D013698:Templates, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D015342:DNA Probes; D004279:DNA, Viral; D014157:Transcription Factors; D005914:Globins