Zehring W A, Lee J M, Weeks J R, Jokerst R S, Greenleaf A L
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1988 Jun;85(11):3698-702. doi: 10.1073/pnas.85.11.3698.
DNA sequence analysis of RpII215, the gene that encodes the Mr215,000 subunit of RNA polymerase II (EC 2.7.7.6) in Drosophila melanogaster, reveals that the 3'-terminal exon includes a region encoding a C-terminal domain composed of 42 repeats of a seven-residue amino acid consensus sequence, Tyr-Ser-Pro-Thr-Ser-Pro-Ser. A hemi- and homozygous lethal P-element insertion into the coding sequence of this domain causes premature translation termination and therefore truncation of the protein, leaving only 20 heptamer repeats. While loss of approximately 50% of the repeat structure in this mutant is a lethal event in vivo, enzyme containing the truncated subunit remains capable of accurate initiation at promoters in vitro. Moreover, treatment of purified intact RNA polymerase II with protease, to remove the entire repeat domain, does not eliminate the enzyme's ability to initiate accurately in vitro. Possible in vivo functions for this unusual protein domain are considered in light of these results.
对果蝇中编码RNA聚合酶II（EC 2.7.7.6）215,000 Mr亚基的基因RpII215进行DNA序列分析，结果显示3'-末端外显子包含一个编码C末端结构域的区域，该结构域由一个七残基氨基酸共有序列Tyr-Ser-Pro-Thr-Ser-Pro-Ser的42个重复序列组成。一个半合子和纯合子致死的P元件插入到该结构域的编码序列中，导致翻译提前终止，从而使蛋白质截短，仅留下20个七聚体重复序列。虽然在该突变体中约50%的重复结构缺失在体内是致死事件，但含有截短亚基的酶在体外仍能够在启动子处准确起始。此外，用蛋白酶处理纯化的完整RNA聚合酶II以去除整个重复结构域，并不会消除该酶在体外准确起始的能力。根据这些结果，我们考虑了这个不寻常蛋白质结构域可能的体内功能。
