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oai:repisalud.isciii.es:20.500.12105/94882025-05-21T07:15:38Zcom_20.500.12105_2052com_20.500.12105_2051col_20.500.12105_19609

00925njm 22002777a 4500 dc Ferrandiz-Avellano, Maria-Jose author Martin-Galiano, Antonio Javier author Schvartzman, Jorge B author de la Campa, Adela G author 2010-06 The transcriptional response of Streptococcus pneumoniae was examined after exposure to the GyrB-inhibitor novobiocin. Topoisomer distributions of an internal plasmid confirmed DNA relaxation and recovery of the native level of supercoiling at low novobiocin concentrations. This was due to the up-regulation of DNA gyrase and the down-regulation of topoisomerases I and IV. In addition, >13% of the genome exhibited relaxation-dependent transcription. The majority of the responsive genes (>68%) fell into 15 physical clusters (14.6-85.6 kb) that underwent coordinated regulation, independently of operon organization. These genomic clusters correlated with AT content and codon composition, showing the chromosome to be organized into topology-reacting gene clusters that respond to DNA supercoiling. In particular, down-regulated clusters were flanked by 11-40 kb AT-rich zones that might have a putative structural function. This is the first case where genes responding to changes in the level of supercoiling in a coordinated manner were found organized as functional clusters. Such an organization revealed DNA supercoiling as a general feature that controls gene expression superimposed on other kinds of more specific regulatory mechanisms. Nucleic Acids Res. 2010 Jun;38(11):3570-81. 10.1093/nar/gkq106 1362-4962 0305-1048 Nucleic acids research 20176571 http://hdl.handle.net/20.500.12105/9488 The genome of Streptococcus pneumoniae is organized in topology-reacting gene clusters