CHARACTERIZATION OF THE PROTEIN PRODUCT ENCODED BY A SPLICING VARIANTOF THE MAREKS-DISEASE VIRUS ECO-Q GENE (MEQ)

In the present study, we report the characterization of a 212-amino-ac id polypeptide encoded by a splicing Variant of the Marek's disease vi rus Eco-Q gene (Meq). This protein, referred to as Meq-sp, contains th e N-terminal 100 amino acids of Meq, which include part of Meq's DNA b inding/dimerization domain, but lacks the transactivation domain of Me q. Thus, Meq-sp was examined for its ability to bind to DNA and act as a transactivator. Results indicated that while Meq and Meq-sp could b oth bind to the AP-1 binding site, the 110 C-terminal amino acid resid ues of Meq-sp lacked the ability to function as a transactivator when fused to the GAL4 (1-147) DNA binding motif. To investigate whether Me q-sp can interact with Meq or with c-jun, protein-protein and protein- DNA interactions in vitro were examined. Results showed that Meq-sp ca n associate with both Meq and c-jun and bind to the AP-1 site with a h igher affinity as a heterodimer with c-jun. These results suggest that Meq-sp could compete with Meq for heterodimer formation with c-jun an d dimer binding to DNA and possibly act as a transdominant negative re gulator of Meq activity in vivo. (C) 1996 Academic Press, Inc.