AMINO-ACID STARVATION AFFECTS INITIATION FREQUENCY OF NUCLEOLAR RNA-POLYMERASE
AMINO-ACID STARVATION AFFECTS INITIATION FREQUENCY OF NUCLEOLAR RNA-POLYMERASE
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DOI：
10.1016/0092-8674(76)90174-4
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发表时间：
1976-01-01
期刊：
影响因子：
64.5
通讯作者：
GRUMMT, F
中科院分区：
文献类型：
--
作者：
GRUMMT, I;SMITH, VA;GRUMMT, F
在小鼠腹水核仁中的核糖体前体RNA的合成来源于细胞饥饿的氨基酸进行了比较，从所有氨基酸的存在下培养的对照细胞的核仁的活性。它表明，剥夺一个单一的必需氨基酸的培养介质中的结果在一个急剧下降的RNA形成能力的分离的核仁的2-3倍。rRNA合成的这种关闭是一个非常快速的过程。半最大失活发生后，只有30分钟。添加氨基酸饥饿的细胞导致快速恢复，这是反映了在分离的核仁的RNA聚合酶活性急剧增加。对这种氨基酸介导的rRNA合成控制的分子机制的研究表明，这种效应不是由RNA链的不同生长速率引起的，而是由体内RNA聚合酶的起始频率改变引起的。然而，在来自在完全培养基中生长的细胞的核仁中，几乎所有的聚合酶都紧密结合在转录复合物中，在加入外源模板后变得活跃的大量“游离”聚合酶存在于来自饥饿细胞的核仁中。
The synthesis of ribosomal precursor RNA in mouse ascites nucleoli derived from cells starved for amino acids is compared with the activity of nucleoli from control cells cultivated in the presence of all amino acids. It is shown that deprivation of a single essential amino acid from the cuiture medium results in a drastic decrease of the RNA-forming capacity of the isolated nucleoli by a factor of 2-3. This switchoff in rRNA synthesis is a very fast process. Half-maximal inactivation occurs after only 30 min. Addition of amino acids to starved cells leads to a rapid recovery, which is reflected by a sharp increase in the RNA polymerase activity of the isolated nucleoli. Studies on the molecular mechanism of this amino acid-mediated control of rRNA synthesis indicate that this effect is not caused by different growth rates of the RNA chains, but rather by an altered initiation frequency of the RNA polymerase in vivo. Whereas in nucleoli derived from cells grown in full medium almost all the polymerase is tightly bound in a transcriptional complex, a high amount of “free” polymerase which becomes active after addition of exogenous template is present in nucleoli from starved cells.