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Functional analysis of a novel DNA binding protein of Streptomyces coelicolor. / Matthew J Aldridge
Swansea University Author: Matthew J, Aldridge
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Secondary metabolism occurs after the main growth phase in Streptomyces. A 'transition phase' occurs to remodel global patterns of gene expression at the onset of physiological and developmental differentiation. Many different signals influence this transition phase, integrating, for examp...
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Secondary metabolism occurs after the main growth phase in Streptomyces. A 'transition phase' occurs to remodel global patterns of gene expression at the onset of physiological and developmental differentiation. Many different signals influence this transition phase, integrating, for example, information on nutritional status, growth rate, and stress responses. Several pleiotropic transcription factors that regulate the transition phase have been identified, but aspects of epigenetic control of gene expression are not well understood. This study focused on the characterisation of a novel gene sco2075 in S. coelicolor encoding a protein that combines a histone-like domain with a conserved DksA-like domain, the latter considered a ppGpp cofactor. The protein is important for integrating responses to both oxidative and osmotic stresses. The sco2075- mutant strain is sensitive to oxidative stress at least in part due to reduced induction of the alternative sigma factor sigmaR. SCO2075, similarly to E. coli DksA, may play a possible role in the liberation of core RNA polymerase to bind alternative sigma factors such as sigmaR. In addition DSCO2075 has an altered topological profile of a reporter plasmid under osmotic stress, showing little alteration in negative supercoiling when compared to the significant increase in wildtype. DSCO2075 also has a reduction in aerial hyphae and a possible reduction in actinorhodin production when grown with osmolyte. The histone-like domain of SCO2075 binds DNA non-specifically. SCO2075 expression appears to coincide with diffused FtsZ expression prior to Z-ring formation when SCO2075 appears to become nucleoid associated. Analysis of pre-spore compartment lengths showed SCO2075 is one of several nucleoid associated proteins involved in nucleoid compaction during aerial hyphal erection and sporulation. Absence of sco2075, however, does not affect the production of unigenomic spore chains. Finally, over-expression of SCO2075 suppresses defects in secondary metabolism of a relA mutant affected in ppGpp synthesis. SCO2075 could potentially be a new type of regulator, likely acting as a node to integrate stress and physiological cues by modulating DNA topology/compaction and RNA polymerase activity.
Swansea University Medical School