Robert-Le Meur M, Portier C
Institute de Biologie Physico-Chimique, Paris, France.
EMBO J. 1992 Jul;11(7):2633-41. doi: 10.1002/j.1460-2075.1992.tb05329.x.
It has been previously shown that the pnp messenger RNAs are cleaved by RNase III at the 5' end and that these cleavages induce a rapid decay of these messengers. A translational fusion between pnp and lacZ was introduced into the chromosome of a delta lac strain to study the expression of pnp. In the presence of increased cellular concentrations of polynucleotide phosphorylase, the level of the hybrid beta-galactosidase is repressed, whereas the synthesis rate of the corresponding message is not significantly affected. In the absence of pnp, the level of the hybrid protein increases strongly. Thus, polynucleotide phosphorylase is post-transcriptionally autocontrolled. However, autocontrol is totally abolished in strains where the RNase III site on the pnp message has been deleted or in strains devoid of RNase III. These results suggest that polynucleotide phosphorylase requires RNase III cleavages to autoregulate the translation of its message. Other mutations in the ribosome binding site region support the hypothesis that this 3' to 5' processive enzyme could recognize a specific repressor binding site at the 5' end of pnp mRNA. Implications of these results on the mechanism of regulation and on messenger degradation are discussed.
先前的研究表明，多核苷酸磷酸化酶（pnp）信使核糖核酸（mRNA）在5'端被核糖核酸酶III（RNase III）切割，这些切割会导致这些信使的快速降解。将pnp与lacZ的翻译融合体导入δlac菌株的染色体中，以研究pnp的表达。在细胞中多核苷酸磷酸化酶浓度增加的情况下，杂交β-半乳糖苷酶的水平受到抑制，而相应信使的合成速率没有受到显著影响。在缺乏pnp的情况下，杂交蛋白的水平强烈增加。因此，多核苷酸磷酸化酶在转录后进行自我调控。然而，在pnp信使上的RNase III位点已被删除的菌株或缺乏RNase III的菌株中，自我调控完全被消除。这些结果表明，多核苷酸磷酸化酶需要RNase III切割来自动调节其信使的翻译。核糖体结合位点区域的其他突变支持这样的假设，即这种3'到5'的进行性酶可以识别pnp mRNA 5'端的特定阻遏物结合位点。讨论了这些结果对调控机制和信使降解的影响。
