The fission yeast RPA21 subunit of RNA polymerase I: an evolutionarily conserved subunit interacting with ribosomal DNA (rDNA) transcription factor Rrn3p for recruitment to rDNA promoter
The fission yeast RPA21 subunit of RNA polymerase I: an evolutionarily conserved subunit interacting with ribosomal DNA (rDNA) transcription factor Rrn3p for recruitment to rDNA promoter
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DOI：
10.1266/ggs.77.147
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发表时间：
2002-06-01
影响因子：
1.1
通讯作者：
Nogi, Y
中科院分区：
文献类型：
--
作者：
Imazawa, Y;Hisatake, K;Nogi, Y
RNA聚合酶在同源启动子上的募集是真核生物中特定基因转录起始的关键步骤。最近，酿酒酵母的RNA聚合酶I（pol I）被证明通过rDNA的保守转录因子Rrn 3 p和pol L特异性亚基A43之间的相互作用被募集到rDNA启动子。pol I募集的类似相互作用在其他真核生物中是否保守的问题仍有待回答。我们发现粟酒裂殖酵母rpa 21（+）编码一个表观分子量为21 kD的蛋白质，与裂殖酵母pol Ⅰ的A43亚基有36%的同源性。rpa 21（+）是细胞生长所必需的。为了进一步了解RPA 21的功能，我们分离了总共22个rpa 21（+）的温度敏感（ts）突变体，发现引起ts表型的大多数取代聚集在RPA 21的N-末端的一半。TS突变体在温度升高后立即显示rDNA初级转录物的量显著减少。S. TS突变体中的粟酒酵母RRN 3（+）以等位基因特异性方式抑制生长缺陷。因此，我们得出结论，S。pombe RPA 21在S. pol I亚基与Rrn 3 p的相互作用将pol I募集到rDNA启动子的机制在进化上是保守的。
Recruitment of RNA polymerases to the cognate promoter is a key step for the transcription initiation of specific genes in eukaryotes. Recently, RNA polymerase I (pol I) of Saccharomyces cerevisiae was shown to be recruited to the rDNA promoter via interaction between Rrn3p, a conserved transcription factor for rDNA, and A43, a subunit specific to pol L The question of whether a similar interaction for pol I recruitment is conserved in other eukaryotes remains to be answered. We show here that Schizosaccharomyces pombe rpa21(+) encodes a protein of apparent molecular mass 21 kD which shows 36% identity to the A43 subunit of pol I in S. cerevisiae, and that rpa21(+) is essential for cell growth. To gain further insight into the functions of RPA21, we isolated a total of 22 temperature-sensitive (ts) mutants of rpa21(+) and found that most of the substitutions causing the ts phenotype are clustered in the N-terminal half of RPA21. The ts mutants showed a markedly reduced amount of primary transcripts of rDNA immediately after temperature shift-up. Over-expression of S. pombe rrn3(+) in the ts mutants suppressed the growth defect in an allele-specific manner. Therefore, we conclude that S. pombe RPA21 plays a functional role similar to that of A43 in S. cerevisiae and that the mechanism of recruitment of pol I to the rDNA promoter by the interaction of a specific pol I subunit with Rrn3p is evolutionarily conserved.