RESUMEN
The effect of novobiocin, a gyrase inhibitor, and of catabolite repression on the expression of different classes of tetA genes in Escherichia coli was studied. The results obtained showed that the complete induction of the tetA genes corresponding to classes A, B, and D depends on DNA supercoiling, and that the expression of the tetA genes corresponding to classes A and C is not under catabolite repression.
Asunto(s)
Proteínas Bacterianas/genética , ADN Superhelicoidal/genética , Escherichia coli/genética , Regulación de la Expresión Génica , Proteínas Represoras/genética , Factores de Transcripción/genética , Secuencia de Bases , ADN Bacteriano/genética , Escherichia coli/efectos de los fármacos , Datos de Secuencia Molecular , Novobiocina/farmacología , Plásmidos , Regiones Promotoras Genéticas , Factores R , Proteínas Represoras/biosíntesis , Resistencia a la TetraciclinaRESUMEN
To further analyze the organization of the nuclear rDNA locus in Trypanosoma cruzi, genomic recombinant plasmid clones were constructed and isolated after hybridization with rRNA molecules as hybridization probes. Approximately 11 kilobase pairs from the cistron were cloned in three recombinant plasmids carrying adjacent genomic fragments. Restriction mapping and Southern hybridization experiments performed on these clones indicate the following relative arrangement of the mature rRNA coding sequences: 18S (2.46 kb), S3 (197 b), 24S alpha (2.02 kb), S1 (261 b), 24 beta (1.66 kb), S2 (217 b) and S6 (90 b). Neither S4 (141 b) nor S5 (110 b) sequences were found within these genomic clones. Nevertheless genomic Southerns suggest a linkage of S4 towards the 3' end of this genetic system.