Differential binding of zinc fingers from Xenopus TFIIIA and p43 to 5S RNA and the 5S RNA gene.

Zinc fingers are usually associated with proteins that interact with DNA. Yet in two oocyte-specific Xenopus proteins, TFIIA and p43, zinc fingers are used to bind 5S RNA. One of these, TFIIIA, also binds the 5S RNA gene. Both proteins have nine zinc fingers that are nearly identical with respect to size and spacing. We have determined the relative affinities of groups of zinc fingers from TFIIIA for both 5S RNA and the 5S RNA gene. We have also determined the relative affinities of groups of zinc fingers from p43 for 5S RNA. The primary protein regions for RNA and DNA interaction in TFIIIA are located at opposite ends of the molecule. All zinc fingers from TFIIIA participate in binding 5S RNA, but zinc fingers from the C terminus have the highest affinity. N-terminal zinc fingers are essential for binding the 5S RNA gene. In contrast, zinc fingers at the amino terminus of p43 are essential for binding 5S RNA.     

一种特异识别SV40启动子的人工转录因子的构建

转录因子是真核表达调控中非常重要的一类反式作用因子,通常由DNA结合域与效应域两部分组成,而锌指结构是DNA结合域的常见组成单元。人工转录因子就是基于转录因子的这种结构特点,人为地选择针对特定序列的DNA结合域与具有特定作用的效应域组合而成。利用噬菌体展示技术,筛选到与SV40启动子上9bp序列特异结合的锌指结构,再连接KOX1的KRAB域构建了一种人工转录因子。转染实验表明它对SV40下游的报告基因的表达有很显著的抑制作用。