Lalo D, Carles C, Sentenac A, Thuriaux P
Département de Biologie Cellulaire et Moléculaire, Centre d'Etudes de Saclay, Gif sur Yvette, France.
Proc Natl Acad Sci U S A. 1993 Jun 15;90(12):5524-8. doi: 10.1073/pnas.90.12.5524.
The AC40 and AC19 subunits (encoded by RPC40 and RPC19) are shared by yeast RNA polymerases I and III and have a local sequence similarity to prokaryotic alpha subunits. Mutational analysis of the corresponding "alpha motif" indicated that its integrity is essential on AC40 subunit but is not essential on AC19 subunit. By applying the two-hybrid method, these two polypeptides were shown to associate in vivo. Extragenic suppression of rpc19 and rpc40 mutations confirmed that AC19 and AC40 subunits interact with each other in vivo and revealed an interaction with ABC10 beta subunit [encoded by RPB10; Woychick, N. A. & Young, R.A. (1990) J. Biol. Chem. 265, 17816-17819], one of the five polypeptides common to all three nuclear RNA polymerases. A correction of the RPB10 sequence showed that ABC10 beta subunit is a 70-amino acid polypeptide, as confirmed by peptide microsequencing. These results suggest that the assembly of RNA polymerase I and III requires the association of ABC10 beta subunit with an AC19/AC40 heterodimer.
AC40和AC19亚基（由RPC40和RPC19编码）为酵母RNA聚合酶I和III所共有，并且在局部序列上与原核α亚基相似。对相应“α模体”的突变分析表明，其完整性对AC40亚基至关重要，但对AC19亚基并非必不可少。通过应用双杂交方法，显示这两种多肽在体内相互关联。rpc19和rpc40突变的基因外抑制证实，AC19和AC40亚基在体内相互作用，并揭示了与ABC10β亚基[由RPB10编码；Woychick, N. A. & Young, R.A. (1990) J. Biol. Chem. 265, 17816 - 17819]的相互作用，ABC10β亚基是所有三种核RNA聚合酶共有的五种多肽之一。对RPB10序列的校正表明，ABC10β亚基是一种70个氨基酸的多肽，肽微测序证实了这一点。这些结果表明，RNA聚合酶I和III的组装需要ABC10β亚基与AC19/AC40异二聚体的关联。
