Epinat J C, Kazandjian D, Harkness D D, Petros S, Dave J, White D W, Gilmore T D
Department of Biology, Boston University, Massachusetts 02215-2406, USA.
Oncogene. 2000 Feb 3;19(5):599-607. doi: 10.1038/sj.onc.1203376.
The retroviral oncoprotein v-Rel is a member of the Rel/ NF-kappaB family of transcription factors. v-Rel has multiple changes as compared to the proto-oncoprotein c-Rel, and these changes render v-Rel highly oncogenic in avian lymphoid cells. Previous results have shown that three mutant residues in the eleven helper virus-derived Envelope (Env) amino acids (aa) at the N-terminus of v-Rel are required for its full oncogenicity. In this report, we show that these mutant Env aa also enable sequences in the N-terminal half of v-Rel to activate transcription in yeast and chicken cells, under conditions where the analogous sequences from c-Rel either do not or only weakly activate transcription. Removal of the Env aa from v-Rel or site-directed mutations that revert the three mutant residues to the residues present in the Rev-A helper virus Env protein abolish this transactivation ability of v-Rel. Addition of mutant Env aa onto c-Rel is not sufficient to fully restore the transactivation function; other sequences in the N-terminal half of v-Rel are needed for full transactivating ability. A C terminally-truncated form of NF-kappaB p100 (p85), produced in HUT-78 human leukemic cells, also activates transcription in yeast, under conditions where the normal p52 and p100 proteins do not. Furthermore, transcriptional activation by p85 in yeast is likely to occur through N-terminal sequences. Taken together, these results are consistent with a model in which transactivation by N-terminal Rel Homology (RH) domain sequences in oncogenic Rel family proteins is influenced by sequences outside the RH domain.
逆转录病毒癌蛋白v-Rel是转录因子Rel/NF-κB家族的成员。与原癌蛋白c-Rel相比,v-Rel有多处变化,这些变化使v-Rel在禽类淋巴细胞中具有高度致癌性。先前的结果表明,v-Rel N端11个源自辅助病毒的包膜(Env)氨基酸中的三个突变残基是其完全致癌性所必需的。在本报告中,我们表明,这些突变的Env氨基酸还能使v-Rel N端一半的序列在酵母和鸡细胞中激活转录,而在相同条件下,c-Rel的类似序列要么不激活转录,要么仅微弱激活转录。从v-Rel中去除Env氨基酸或通过定点突变将三个突变残基恢复为Rev-A辅助病毒Env蛋白中的残基,会消除v-Rel的这种反式激活能力。将突变的Env氨基酸添加到c-Rel上不足以完全恢复反式激活功能;v-Rel N端一半的其他序列对于完全的反式激活能力是必需的。在HUT-78人白血病细胞中产生的NF-κB p100(p85)的C端截短形式,在正常p52和p100蛋白不激活转录的条件下,也能在酵母中激活转录。此外,p85在酵母中的转录激活可能通过N端序列发生。综上所述,这些结果与一个模型一致,即致癌性Rel家族蛋白中N端Rel同源(RH)结构域序列的反式激活受RH结构域之外的序列影响。