Lin-Chao S, Cohen S N
Institute of Molecular Biology, Academia Sinica, Nankang Taipei, Taiwan, Republic of China.
Cell. 1991 Jun 28;65(7):1233-42. doi: 10.1016/0092-8674(91)90018-t.
We show that the rate of degradation of RNAI, an anti-sense repressor of the replication primer RNAII, is a key element of control in the replication of ColE1-type plasmids in vivo. Cleavage of RNAI by RNAase E, a ribosomal RNA-processing enzyme encoded or controlled by the rne (also known as ams) locus, relieves repression by endonucleolytically converting RNAI to a very rapidly decaying product, pRNAI-5. A 5' triphosphate-terminated homolog of pRNAI-5 is degraded slowly and consequently inhibits replication. Nucleotide substitutions within the RNAase E cleavage sequence alter RNAI half-life and plasmid copy number, changing also the incompatibility phenotype. RNAI variants lacking the sequence cleaved by RNAase E are eliminated by growth rate-dependent degradation, resulting in growth-responsive control of plasmid replication and copy number.
我们发现，RNAI（复制引物RNAII的反义阻遏物）的降解速率是体内ColE1型质粒复制控制的关键因素。由rne（也称为ams）位点编码或控制的核糖体RNA加工酶RNAase E对RNAI的切割，通过内切核酸酶将RNAI转化为一种快速降解的产物pRNAI-5，从而解除抑制作用。pRNAI-5的5'三磷酸末端同源物降解缓慢，因此会抑制复制。RNAase E切割序列内的核苷酸取代会改变RNAI的半衰期和质粒拷贝数，同时也会改变不相容表型。缺乏RNAase E切割序列的RNAI变体通过生长速率依赖性降解被消除，从而实现对质粒复制和拷贝数的生长响应控制。
