Imai K, Imazawa Y, Yao Y, Yamamoto K, Hisatake K, Muramatsu M, Nogi Y
Department of Biochemistry, Saitama Medical School, Iruma-Gun, Japan.
Mol Gen Genet. 1999 Mar;261(2):364-73. doi: 10.1007/s004380050977.
Eukaryotic RNA polymerases I and III consist of multiple subunits. Each of these enzymes includes two distinct and evolutionarily conserved subunits called alpha-related subunits which are shared only by polymerases I and III. The alpha-related subunits show limited homology with the alpha-subunit of prokaryotic RNA polymerase. To gain further insight into the structure and function of alpha-related subunits, we cloned and characterized a gene from Schizosaccharomyces pombe that encodes a protein of 17 kDa which can functionally replace AC19 - an alpha-related subunit of RNA polymerases I and III of Saccharomyces cerevisiae - and was thus named rpa17+. RPA17 has 125 amino acids and shows 63% identity to AC19 over a 108-residue stretch, whereas the N-terminal regions of the two proteins are highly divergent. Disruption of rpa17+ shows that the gene is essential for cell growth. Sequence comparison with other alpha-related subunits from different species showed that RPA17 contains an 81-amino acid block that is evolutionarily conserved. Deletion analysis of the N- and C-terminal regions of RPA17 and AC19 confirms that the 81-amino acid block is important for the function of the alpha-related subunits.
真核生物RNA聚合酶I和III由多个亚基组成。这些酶中的每一种都包含两个不同的且在进化上保守的亚基，称为α相关亚基，它们仅由聚合酶I和III共享。α相关亚基与原核生物RNA聚合酶的α亚基显示出有限的同源性。为了进一步深入了解α相关亚基的结构和功能，我们从粟酒裂殖酵母中克隆并鉴定了一个基因，该基因编码一种17 kDa的蛋白质，它可以在功能上替代AC19（酿酒酵母RNA聚合酶I和III的一种α相关亚基），因此被命名为rpa17+。RPA17有125个氨基酸，在108个残基的区域内与AC19有63%的同一性，而这两种蛋白质的N端区域高度不同。rpa17+的破坏表明该基因对细胞生长至关重要。与来自不同物种的其他α相关亚基的序列比较表明，RPA17包含一个在进化上保守的81个氨基酸的区域。对RPA17和AC19的N端和C端区域的缺失分析证实，这个81个氨基酸的区域对α相关亚基的功能很重要。
