Nucleoid-Associated Proteins of Streptomyces coelicolor: Discovery and Functions

The regulation of gene expression from biosynthetic gene clusters is a key concern in natural product discovery as these clusters are often transcriptionally silent (“cryptic”) under normal laboratory conditions, making the initial characterisation and heterologous expression of the products they encode problematic. The role of the architectural nucleoid-associated proteins (NAPs) in regulation of the expression of these products has been neglected within the Actinomycetes. NAPs are small, highly abundant proteins which govern both gene expression and nucleoid structure on a genome-wide scale. A method for surveying the proteome of the S. coelicolor nucleoid was developed which generated a list of 25 proteins with a high probability of being NAPs. This list included known NAPs such as HupA, HupS, Lsr2 and sIHF and the known global regulators CRP and BldD, as well as a number of interesting novel NAP candidates from a variety of protein classes suitable for further investigation. One of these proteins, SCO5592, was investigated as a candidate global RNA-binding regulator. It was found to comprise a KH domain with an N-terminal extension and formed oligomers of 10 - 12 subunits in solution. The mutant phenotypes of both S. coelicolor paralogs of HU (HupA and HupS) were examined and showed opposite effects on growth, spore formation and actinorhodin production. The mutant phenotypes of both S. coelicolor paralogs of the H-NS-like proteins Lsr2 (SCO3375 and SCO4076) were milder and showed a greater degree of overlap than the HU mutants, however both showed a moderate abnormality in spore morphology, suggesting that they have a role in spore nucleoid segregation. Phylogenetic analysis of the HU and Lsr2 proteins revealed that the lysine-rich tail domain of HupS was acquired after the HupA and HupS core domains had begun to diverge and that lysine-rich sequences have evolved multiple times.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of East Anglia

Year dc:date.issued

2013

Author dc:creator

• Bradshaw, Elizabeth Helen

Language dc:language

en