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Disruption of largest subunit RNA polymerase II genes in Trypanosoma brucei. 总被引:4,自引:1,他引:3
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H M Chung M G Lee P Dietrich J Huang L H Van der Ploeg 《Molecular and cellular biology》1993,13(6):3734-3743
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In vitro analysis of alpha-amanitin-resistant transcription from the rRNA, procyclic acidic repetitive protein, and variant surface glycoprotein gene promoters in Trypanosoma brucei.
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Gabriele Laufer Gabriel Schaaf Sigrid Bollgnn Arthur Günzl 《Molecular and cellular biology》1999,19(8):5466-5473
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VSG gene 118 is transcribed from a cotransposed pol I-like promoter 总被引:31,自引:0,他引:31
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While growing in the tsetse fly, Trypanosoma brucei expresses a major surface glycoprotein, the procyclic acidic repetitive protein (PARP). The parp genes are transcribed by an alpha-amanitin-resistant RNA polymerase. We have determined the sequence requirements for parp promoter activity. Studies of RNA produced from input DNA in transiently transfected trypanosomes indicate that the RNA is correctly processed by trans-splicing and polyadenylation. Deletion analyses show that 330 bp are sufficient for full promoter and splicing activity and that the promoter structure is complex, involving at least three elements whose mutual spacing is important. Mutagenesis pin-pointed two sequences vital for promoter activity; neither bears any resemblance to known prokaryotic or eukaryotic promoter elements. 相似文献
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A controversy has surrounded the questions of whether or not guanosine tetraphosphate (ppGpp) is a specific inhibitor of bacterial rRNA and tRNA synthesis, especially during normal exponential growth, and whether the RNA polymerase is the target of ppGpp action. To answer these questions, a pBR322-derived plasmid, pKT28, was constructed that carries the Escherichia coli relA gene encoding a ppGpp synthetase under control of the lacUV5 promoter. The plasmid was used to transform the ppGpp reporter strain VH271 in which expression of beta-galactosidase from an rrnB P1 promoter is inhibited by ppGpp. In the presence of high concentrations of lac inducer, bacteria of the transformed strain accumulate ppGpp with the result that synthesis of rRNA and beta-galactosidase is inhibited and growth ceases. At low concentrations of inducer, growth is only reduced and cells form small white colonies on X-gal indicator plates. After continued incubation, these colonies form blue sectors of faster growing mutant cells. Phage P1 transduction experiments showed that these mutants have mutations cotransducing with rpoB, the gene encoding the beta-subunit of RNA polymerase. One particular mutant strain, KT13, had acquired partial resistance to ppGpp inhibition of rRNA synthesis. The mutation in this strain was cloned by in vivo recombination into an rpoB plasmid. The presence of this plasmid conferred increased resistance to overproduction of ppGpp. These results suggest that ppGpp is a specific inhibitor of rRNA synthesis, even in the absence of amino acid starvation, and that RNA polymerase is involved as the target of ppGpp action. 相似文献
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