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A novel bifunctional histone protein in Streptomyces: a candidate for structural coupling between DNA conformation and transcription during development and stress?

Aldridge M, Facey P, Francis L, Bayliss S, Del Sol R, Dyson P - Nucleic Acids Res. (2013)

Bottom Line: Here, we describe a novel developmentally regulated nucleoid-associated protein, DdbA, of the genus that consists of an N-terminal DNA-binding histone H1-like domain and a C-terminal DksA-like domain that can potentially modulate RNA polymerase activity in conjunction with ppGpp.The mutant is also sensitive to oxidative stress owing to impaired upregulation of transcription of sigR, encoding an alternative sigma factor.Consequently, we propose this bifunctional histone-like protein as a candidate that could structurally couple changes in DNA conformation and transcription during the streptomycete life-cycle and in response to stress.

View Article: PubMed Central - PubMed

Affiliation: Institute of Life Science, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.

ABSTRACT
Antibiotic-producing Streptomyces are complex bacteria that remodel global transcription patterns and their nucleoids during development. Here, we describe a novel developmentally regulated nucleoid-associated protein, DdbA, of the genus that consists of an N-terminal DNA-binding histone H1-like domain and a C-terminal DksA-like domain that can potentially modulate RNA polymerase activity in conjunction with ppGpp. Owing to its N-terminal domain, the protein can efficiently bind and condense DNA in vitro. Loss of function of this DNA-binding protein results in changes in both DNA condensation during development and the ability to adjust DNA supercoiling in response to osmotic stress. Initial analysis of the DksA-like activity of DdbA indicates that overexpression of the protein suppresses a conditional deficiency in antibiotic production of relA mutants that are unable to synthesise ppGpp, just as DksA overexpression in Escherichia coli can suppress ppGpp(0) phenotypes. The mutant is also sensitive to oxidative stress owing to impaired upregulation of transcription of sigR, encoding an alternative sigma factor. Consequently, we propose this bifunctional histone-like protein as a candidate that could structurally couple changes in DNA conformation and transcription during the streptomycete life-cycle and in response to stress.

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In vitro condensation of plasmid DNA by DdbA. Panel A: Atomic Force Microscopy image (Height) of DdbA bound to circular pUC18 plasmid. Panel B shows enlargements of a large-, an intermediate- and a smaller-sized protein–DNA aggregate. Panel C illustrates circular pUC18 (negative control).
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gkt180-F4: In vitro condensation of plasmid DNA by DdbA. Panel A: Atomic Force Microscopy image (Height) of DdbA bound to circular pUC18 plasmid. Panel B shows enlargements of a large-, an intermediate- and a smaller-sized protein–DNA aggregate. Panel C illustrates circular pUC18 (negative control).

Mentions: Recombinant DdbA was also observed to condense supercoiled plasmid DNA in vitro. Atomic force microscopy of protein–DNA assemblies revealed different sized complexes of multiple plasmid molecules condensed with oligomeric protein (Figure 4), resembling electron micrograph images of other histone H1-like proteins condensed with plasmid DNA (28).Figure 4.


A novel bifunctional histone protein in Streptomyces: a candidate for structural coupling between DNA conformation and transcription during development and stress?

Aldridge M, Facey P, Francis L, Bayliss S, Del Sol R, Dyson P - Nucleic Acids Res. (2013)

In vitro condensation of plasmid DNA by DdbA. Panel A: Atomic Force Microscopy image (Height) of DdbA bound to circular pUC18 plasmid. Panel B shows enlargements of a large-, an intermediate- and a smaller-sized protein–DNA aggregate. Panel C illustrates circular pUC18 (negative control).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3643593&req=5

gkt180-F4: In vitro condensation of plasmid DNA by DdbA. Panel A: Atomic Force Microscopy image (Height) of DdbA bound to circular pUC18 plasmid. Panel B shows enlargements of a large-, an intermediate- and a smaller-sized protein–DNA aggregate. Panel C illustrates circular pUC18 (negative control).
Mentions: Recombinant DdbA was also observed to condense supercoiled plasmid DNA in vitro. Atomic force microscopy of protein–DNA assemblies revealed different sized complexes of multiple plasmid molecules condensed with oligomeric protein (Figure 4), resembling electron micrograph images of other histone H1-like proteins condensed with plasmid DNA (28).Figure 4.

Bottom Line: Here, we describe a novel developmentally regulated nucleoid-associated protein, DdbA, of the genus that consists of an N-terminal DNA-binding histone H1-like domain and a C-terminal DksA-like domain that can potentially modulate RNA polymerase activity in conjunction with ppGpp.The mutant is also sensitive to oxidative stress owing to impaired upregulation of transcription of sigR, encoding an alternative sigma factor.Consequently, we propose this bifunctional histone-like protein as a candidate that could structurally couple changes in DNA conformation and transcription during the streptomycete life-cycle and in response to stress.

View Article: PubMed Central - PubMed

Affiliation: Institute of Life Science, College of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK.

ABSTRACT
Antibiotic-producing Streptomyces are complex bacteria that remodel global transcription patterns and their nucleoids during development. Here, we describe a novel developmentally regulated nucleoid-associated protein, DdbA, of the genus that consists of an N-terminal DNA-binding histone H1-like domain and a C-terminal DksA-like domain that can potentially modulate RNA polymerase activity in conjunction with ppGpp. Owing to its N-terminal domain, the protein can efficiently bind and condense DNA in vitro. Loss of function of this DNA-binding protein results in changes in both DNA condensation during development and the ability to adjust DNA supercoiling in response to osmotic stress. Initial analysis of the DksA-like activity of DdbA indicates that overexpression of the protein suppresses a conditional deficiency in antibiotic production of relA mutants that are unable to synthesise ppGpp, just as DksA overexpression in Escherichia coli can suppress ppGpp(0) phenotypes. The mutant is also sensitive to oxidative stress owing to impaired upregulation of transcription of sigR, encoding an alternative sigma factor. Consequently, we propose this bifunctional histone-like protein as a candidate that could structurally couple changes in DNA conformation and transcription during the streptomycete life-cycle and in response to stress.

Show MeSH
Related in: MedlinePlus