The PKC targeting protein RACK1 interacts with the Epstein-Barr virus activator protein BZLF1 (original) (raw)
2000, European Journal of Biochemistry
Phorbol esters reactivate Epstein±Barr virus (EBV) from latently infected cells via transcriptional activation of the viral immediate-early gene BZLF1. BZLF1 is a member of the extended AP-1 family of transcription factors that binds to specific BZLF1-binding motifs within early EBV promoters and to consensus AP-1 sites. Regulation of BZLF1's activity is achieved at the transcriptional level as well as through post-translational modifications. Recently, we reported that the transcriptional activity of BZLF1 is augmented by TPA [Baumann, M., Mischak, H.]. The increase of BZLF1's activity depends on a single serine residue (S186) that is phosphorylated by protein kinase C (PKC) in vitro and in vivo after stimulation with 12-Otetradecanoylphorbol-13-acetate (TPA). Here, we identified RACK1 as a binding partner of BZLF1 in a yeast interaction trap assay. RACK stands for receptor of activated C-kinase and is involved in targeting activated PKCs and other signaling proteins. In vivo, RACK1 binds directly to the transactivation domain of BZLF1. Although a functional relationship between BZLF1 and PKC could be mediated by RACKs, RACK1 did not have a detectable effect on the phosphorylation status of BZLF1 in in vitro or in vivo phosphorylation assays. We suggest that RACK1 may act as a scaffolding protein on BZLF1 independently of activated PKCs. q FEBS 2000 RACK1 and BZLF1 interact (Eur. J. Biochem. 267) 3893 q FEBS 2000 RACK1 and BZLF1 interact (Eur. J. Biochem. 267) 3895 q FEBS 2000 RACK1 and BZLF1 interact (Eur. J. Biochem. 267) 3897 Fig. 6. Detection of wild-type and mutant BZLF1 in various cellular compartments. 293 cells were transfected with pCMV:BZLF1(wt) or pCMV:BZLF1(D26±88). Following preparation of whole cell extracts and cytoplasmic and nuclear fractions, respectively, BZLF1 was detected by immunostaining with a BZLF1-specific antibody. q FEBS 2000 RACK1 and BZLF1 interact (Eur. J. Biochem. 267) 3899
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