Intragenic and extragenic suppressors of mutations in the heptapeptide repeat domain of Saccharomyces cerevisiae RNA polymerase II.
Intragenic and extragenic suppressors of mutations in the heptapeptide repeat domain of Saccharomyces cerevisiae RNA polymerase II.
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作者：
M. Nonet;R. Young
RNA聚合酶II的最大亚基在其羧基端含有一个重复的七肽序列。具有某些羧基末端重复序列（CTR）区域部分缺失的酵母菌突变体对温度敏感，对冷敏感，并且是肌醇营养不良。分离出冷敏感型CTR结构域缺失突变体的基因内和基因外抑制子，研究该结构域的功能。两种基因内抑制突变抑制CTR结构域缺失突变体的温度敏感性、冷敏感性和肌醇萎缩。大多数基因内突变通过复制重复编码序列的不同部分来扩大重复结构域。其他基因内抑制突变是大亚基保守片段中的点突变。一个基因外抑制突变（SRB2-1）被分离出来，强烈抑制CTR结构域突变的条件和营养不良表型。分离并定位SRB2基因，构建了SRB2部分缺失突变（SRB2 delta 10）。srb2 δ 10突变体对温度敏感，对寒冷敏感，并且是肌醇营养不良。这些表型是编码转录装置成分的基因突变的特征。我们提出SRB2基因编码一个参与RNA合成的因子，并可能与RNA聚合酶II大亚基的CTR结构域相互作用。
The largest subunit of RNA polymerase II contains a repeated heptapeptide sequence at its carboxy terminus. Yeast mutants with certain partial deletions of the carboxy-terminal repeat (CTR) domain are temperature-sensitive, cold-sensitive and are inositol auxotrophs. Intragenic and extragenic suppressors of the cold-sensitive phenotype of CTR domain deletion mutants were isolated and studied to investigate the function of this domain. Two types of intragenic suppressing mutations suppress the temperature-sensitivity, cold-sensitivity and inositol auxotrophy of CTR domain deletion mutants. Most intragenic mutations enlarge the repeat domain by duplicating various portions of the repeat coding sequence. Other intragenic suppressing mutations are point mutations in a conserved segment of the large subunit. An extragenic suppressing mutation (SRB2-1) was isolated that strongly suppresses the conditional and auxotrophic phenotypes of CTR domain mutations. The SRB2 gene was isolated and mapped, and an SRB2 partial deletion mutation (srb2 delta 10) was constructed. The srb2 delta 10 mutants are temperature-sensitive, cold-sensitive and are inositol auxotrophs. These phenotypes are characteristic of mutations in genes encoding components of the transcription apparatus. We propose that the SRB2 gene encodes a factor that is involved in RNA synthesis and may interact with the CTR domain of the large subunit of RNA polymerase II.