Witmer H, Baros A, Ende D, Dosmar M
J Virol. 1976 Sep;19(3):846-56. doi: 10.1128/JVI.19.3.846-856.1976.
A 30 degrees C, functional messengers for dCMP hydroxymethylase first appeared 3 to 6 min postinfection and reached their maximum levels at 12 min. Chloramphenicol, added before the phage, reduced the rate of mRNA accumulation. When the antibiotic was added 6 min postinfection, mRNA levels increased at their normal rate but there was no obvious repression of messenger accumulation. Delaying the addition of drug until 8 or 12 min had progressively less effect on the pattern of hydroxymethylase mRNA metabolism. When chloramphenicol was present from preinfection times or from 6 min postinfection, all hydroxymethylase mRNA's synthesized were stable; at later times, however, the ability of the drug to stabilize mRNA decreased with its ability to delay the turnoff of mRNA production. An overaccumulation of hydroxymethylase mRNA was also seen when phage-specific DNA synthesis was inhibited either by mutational lesion in an essential viral gene or by 5-fluorodeoxyuridine. By min 20 of a DNA-negative program, hydroxymethylase mRNA synthesis was repressed to the point where it no longer compensated for decay. However, a finite level of hydroxymethylase mRNA synthesis was maintained at later times of a DNA-negative infection. Such results indicate that replication of the phage chromosome is necessary but not sufficient for a complete turnoff of hydroxymethylase mRNA production. Functions controlled by the maturation-defective proteins (the products of genes 55 and 33) played only a minor role in the regulation of hydroxymethylase mRNA, metabolism. Thus, we favor the hypothesis that a complete turnoff of hydroxymethylase messenger production requires one or more new proteins as well as an interval of DNA replication. The absence of DNA synthesis had no particular effect upon dihydrofolate reductase messenger production. The preinfection addition of chloramphenicol likewise had little effect on dihydrofolate reductase messenger metabolism. These latter data imply that prior synthesis of a phage-coded protein synthesis may not be required for the turnoff of reductase messenger production.
在30摄氏度时，脱氧胞苷酸羟甲基化酶的功能性信使在感染后3至6分钟首次出现，并在12分钟时达到最高水平。在噬菌体之前添加氯霉素会降低mRNA积累的速率。当在感染后6分钟添加抗生素时，mRNA水平以正常速率增加，但信使积累没有明显的抑制作用。将药物添加延迟至8或12分钟对羟甲基化酶mRNA代谢模式的影响逐渐减小。当从感染前或感染后6分钟开始存在氯霉素时，所有合成的羟甲基化酶mRNA都是稳定的；然而，在后期，药物稳定mRNA的能力随着其延迟mRNA产生关闭的能力而下降。当通过必需病毒基因中的突变损伤或5-氟脱氧尿苷抑制噬菌体特异性DNA合成时，也会出现羟甲基化酶mRNA的过度积累。到DNA阴性程序的20分钟时，羟甲基化酶mRNA合成被抑制到不再能补偿衰变的程度。然而，在DNA阴性感染的后期维持了有限水平的羟甲基化酶mRNA合成。这些结果表明，噬菌体染色体的复制对于完全关闭羟甲基化酶mRNA的产生是必要的，但不是充分的。由成熟缺陷蛋白（基因55和33的产物）控制的功能在羟甲基化酶mRNA代谢的调节中仅起次要作用。因此，我们支持这样的假设，即完全关闭羟甲基化酶信使的产生需要一种或多种新蛋白质以及一段时间的DNA复制。DNA合成的缺失对二氢叶酸还原酶信使的产生没有特别影响。感染前添加氯霉素同样对二氢叶酸还原酶信使代谢影响很小。这些后期数据表明，还原酶信使产生的关闭可能不需要噬菌体编码的蛋白质合成的预先合成。
