BZLF1 (ZEBRA, Zta) protein of Epstein-Barr virus selected in a yeast one-hybrid system by binding to a consensus site in the IgH intronic enhancer: a role in immunoglobulin expression?
We have used a yeast one hybrid screen to search for factors interacting with a subsegment of the immunoglobulin heavy chain (IgH) intronic enhancer. The 51 bp enhancer segment harbored a so-called E-box and an octamer site, known to bind helix-loop-helix transcription factors and Oct factors, respectively. Mammalian Oct-2A protein was also expressed in yeast, to select for transcription factors possibly cooperating with Oct-2. Six strongly interacting protein clones were selected from a peripheral blood lymphocyte library. These included a B cell-specific co-activator, termed Bob1, that directly binds to Oct-2 (Gstaiger et al., 1995, Nature 373, 360-362). Three further clones represent the helix-loop factors ITF-1 and ITF-2, another one the nucleolar protein nucleophosmin, or B23. Unexpectedly, the sixth clone with strong activity encoded the BZLF1 (= ZLF1, zta, ZEBRA, EB1) protein of Epstein-Barr virus (EBV). BZLF1 is a leucine zipper-related transcription factor and induces the switch from viral latency to lytic growth. We found that BZLF1 also activated transcription in transiently transfected mammalian cells via a consensus binding site located within the IgH intron enhancer. BZLF1 may thus influence immunoglobulin heavy chain expression in EBV-infected B lymphocytes.
Gstaiger
M
M
Institut für Molekularbiologie (II) der Universität Zürich-Irchel, Switzerland.
Hovens
C
C
Georgiev
O
O
Knoepfel
L
L
Schaffner
W
W
D016384:Consensus Sequence; D004742:Enhancer Elements, Genetic; D006367:HeLa Cells; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007438:Introns; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D007143:Immunoglobulin Heavy Chains