Messenger RNA (mRNA) represents a small percentage of RNAs in a cell, with ribosomal RNA (rRNA) making up the bulk of it. To isolate mRNA from eukaryotes, typically poly-A selection is carried out. Recently, a 5´-phosphate-dependent, 5´→3´ processive exonuclease called Terminator has become available. It will digest only RNA that has a 5´-monophosphate end and therefore it is very useful to eliminate most of rRNAs in cell. We have found that in the pathogenic yeast Candida albicans, while 18S and 25S components isolated from yeast in robust growth phase are easily eliminated by Terminator, those isolated from cells in the nutritionally diminished stationary phase, become resistant to digestion by this enzyme. Additional digestions with alkaline phosphatase, tobacco pyrophosphatase combined with Terminator point toward the 5′-prime end of 18S and 25S as the source of this resistance. Inhibition of TOR by rapamycin also induces resistance by these molecules. We also find that these molecules are incorporated into the ribosome and are not just produced incidentally. Finally, we show that three other yeasts show the same behavior. Digestion of RNA by Terminator has revealed 18S and 25S rRNA molecules different from the accepted processed ones seen in ribosome generation. The reason for these molecules and the underlying mechanism for their formation is unknown. The preservation of this behavior across these yeasts suggests a useful biological role for it, worthy of further inquiry.

中文翻译：

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营养物质的消耗和TOR抑制在白色念珠菌和其他酵母中诱导对5'-磷酸盐依赖性核酸外切酶有抗性的18S和25S核糖体RNA。

信使RNA（mRNA）代表细胞中一小部分RNA，核糖体RNA（rRNA）占了大部分。为了从真核生物中分离mRNA，通常进行poly-A选择。最近，一种称为终止子的依赖5´-磷酸的5´→3´进行性核酸外切酶问世。它只会消化末端带有5´-单磷酸的RNA，因此消除细胞中的大多数rRNA非常有用。我们已经发现，在致病性酵母白色念珠菌中，虽然从处于健壮的生长期的酵母中分离出的18S和25S成分很容易被Terminator消除，但从营养减少的固定相中的细胞中分离出的那些却变得对这种酶具有抵抗力。用碱性磷酸酶进行其他消化，烟草焦磷酸酶与终结剂的结合指向18S和25S的5'-prime端，作为这种抗药性的来源。雷帕霉素对TOR的抑制也诱导了这些分子的抗性。我们还发现，这些分子被并入核糖体中，而不仅仅是偶然产生的。最后，我们证明了其他三种酵母菌也表现出相同的行为。终止子对RNA的消化揭示了18S和25S rRNA分子与核糖体世代中所接受的已加工分子不同。这些分子的原因及其形成的潜在机制尚不清楚。这些酵母中这种行为的保留表明了其有用的生物学作用，值得进一步探讨。我们还发现这些分子被并入核糖体中，而不仅仅是偶然产生的。最后，我们证明了其他三种酵母菌也表现出相同的行为。终止子对RNA的消化揭示了18S和25S rRNA分子与核糖体世代中所接受的已加工分子不同。这些分子的原因及其形成的潜在机制尚不清楚。这些酵母中这种行为的保留表明了其有用的生物学作用，值得进一步探讨。我们还发现，这些分子被并入核糖体中，而不仅仅是偶然产生的。最后，我们证明了其他三种酵母菌也表现出相同的行为。终止子对RNA的消化揭示了18S和25S rRNA分子与核糖体世代中所接受的已加工分子不同。这些分子的原因及其形成的潜在机制尚不清楚。这些酵母中这种行为的保留表明了其有用的生物学作用，值得进一步探讨。这些分子的原因及其形成的潜在机制尚不清楚。这些酵母中这种行为的保留表明了其有用的生物学作用，值得进一步探讨。这些分子的原因及其形成的潜在机制尚不清楚。这些酵母中这种行为的保留表明了其有用的生物学作用，值得进一步探讨。