Hinton D M
Section on Nucleic Acid Biochemistry, National Institute of Diabetes and Digestive and Kidney Disease, Bethesda, Maryland 20892.
J Biol Chem. 1989 Aug 25;264(24):14440-6.
Bacteriophage T4 gene 41 protein is an essential replication protein, part of the primase-helicase required for lagging strand DNA synthesis. In a T4+ infection, 41 RNA is first expressed as a polycistronic transcript attached to the upstream RNA of genes uvsX (recombination protein) and 40 (stimulates head formation (Hinton, D. M. (1989) J. Biol. Chem. 264, 14432-14439). As infection proceeds, less of the upstream RNA extends into gene 41 due to an RNA 3' end, approximately equal to 60 bases downstream of uvsX. DNA sequence analysis of this region positions this end within gene 40, immediately after a GC-rich hairpin. This end probably arises from host factor-dependent transcription termination or RNA processing since it is observed in RNA expressed by a uvsX-40-41 plasmid in vivo, but is not seen after in vitro transcription with purified Escherichia coli RNA polymerase. The E. coli transcription termination (rho) mutant rho026 has been characterized as a rho mutation whose terminating activity is not effectively overcome by phage lambda antitermination (Das, A., Gottesman, M. E., Wardwell, J., Trisler, P., and Gottesman, S. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 5530-5534). During a T4+ abortive infection of rho026, the levels of some phage proteins, including 41, are depressed; a T4 phage mutant in goF gives wild type protein patterns in rho026 (Stitt, B. L., and Mosig, G. (1989) J. Bacteriol., in press). The RNA analyses presented here demonstrate that the severalfold decrease in 41 protein in rho026 is accompanied by a similar decrease in 41 RNA. There is both a general reduction in polycistronic uvsX-40-41 RNA and a 2-2.5-fold increase in the proportion of uvsX RNA ending at the 3' end. Infection of rho026 by T4 goF1 returns the relative amount of RNA reading into 41 versus that stopped to near a wild type level. These results suggest that host rho and the T4 goF are involved in the expression of T4 41 RNA.
噬菌体T4基因41蛋白是一种必需的复制蛋白，是滞后链DNA合成所需的引发酶 - 解旋酶的一部分。在T4 +感染中，41 RNA首先作为多顺反子转录本表达，该转录本与uvsX（重组蛋白）和40（刺激头部形成）基因的上游RNA相连（Hinton，D.M.（1989）J.Biol.Chem.264，14432 - 14439）。随着感染的进行，由于RNA 3'末端（大约在uvsX下游60个碱基处），上游RNA延伸到基因41的部分减少。该区域的DNA序列分析将此末端定位在基因40内，紧接在富含GC的发夹之后。这个末端可能源于宿主因子依赖性转录终止或RNA加工，因为它在体内由uvsX - 40 - 41质粒表达的RNA中观察到，但在用纯化的大肠杆菌RNA聚合酶进行体外转录后未观察到。大肠杆菌转录终止（rho）突变体rho026已被表征为一种rho突变，其终止活性不能被噬菌体λ抗终止有效克服（Das，A.，Gottesman，M.E.，Wardwell，J.，Trisler，P.，和Gottesman，S.（1983）Proc.Natl.Acad.Sci.U.S.A.80，5530 - 5534）。在rho026的T4 +流产感染期间，包括41在内的一些噬菌体蛋白的水平降低；goF中的T4噬菌体突变体在rho026中产生野生型蛋白模式（Stitt，B.L.，和Mosig，G.（1989）J.Bacteriol.，即将发表）。此处呈现的RNA分析表明，rho026中41蛋白的几倍下降伴随着41 RNA的类似下降。多顺反子uvsX - 40 - 41 RNA普遍减少，并且在3'末端结束的uvsX RNA比例增加2 - 2.5倍。T4 goF1对rho026的感染使读入41的RNA与停止的RNA的相对量恢复到接近野生型水平。这些结果表明宿主rho和T4 goF参与了T4 41 RNA的表达。
