A novel function of Streptomyces integration host factor (sIHF) in the control of antibiotic production and sporulation in Streptomyces coelicolor

Abstract

Bacterial integration host factors (IHFs) play important roles in site-specific recombination, DNA replication, transcription, genome organization and bacterial pathogenesis. In Streptomyces coelicolor, there are three putative IHFs: SCO1480, SCO2950 and SCO5556. SCO1480 or Streptomyces IHF (sIHF) was previously identified as a transcription factor that binds to the promoter region of redD, the pathway-specific regulatory gene for the undecylprodigiosin biosynthetic gene cluster. Here we show that production of the pigmented antibiotics actinorhodin and undecylprodigiosin is strongly enhanced in sihf null mutants, while sporulation was strongly inhibited, with an on average 25% increase in spore size. Furthermore, the sihf mutant spores showed strongly reduced viability, with high sensitivity to heat and live/dead staining revealing a high proportion of empty spores, while enhanced expression of sIHF increased viability. This suggests a major role for sIHF in controlling viability, perhaps via the control of DNA replication and/or segregation. Proteomic analysis of the sihf null mutant identified several differentially expressed transcriptional regulators, indicating that sIHF may have an extensive response regulon. These data surprisingly reveal that a basic architectural element conserved in many actinobacteria such as mycobacteria, corynebacteria, streptomycetes and rhodococci may act as a global regulator of secondary metabolism and cell development.

Taxonomy, Physiology, and Natural Products of Actinobacteria

“…FtsK helps to avoid "guillotining" of the DNA by pumping chromosomes into the spore compartments prior to septum closure, and ftsK mutants frequently generate spores with incomplete chromosomes (302)(303)(304). Other proteins that should be considered are SmeA and SffA, which play key roles in DNA translocation during sporulation (302), and also the DNA-packaging proteins HupS (305), sIHF (306,307), Smc (308), and Dps (309).…”

Deciphering the Regulon of Streptomyces coelicolor AbrC3, a Positive Response Regulator of Antibiotic Production

“…Several transcriptional regulators whose genes were downregulated in our study could be responsible for the morphological phenotype observed in the ⌬abrC3 mutant, including sIHF, which also binds to the bldD promoter, a key regulator of development in S. coelicolor (16); the extracytoplasmic function sigma factor WblE (20,21); and BdtA, a putative transcription factor regulated by BldD and involved in morphological differentiation (22,23).…”

“…Of the 32 genes that showed significantly reduced expression in the mutant strain, 16 corresponded to the entire act cluster, including actII-ORF4 (SCO5085), which encodes the SARP pathway-specific regulator of the act cluster (Table 1). Three other significantly downregulated genes, i.e., the sIHF gene (SCO1480) (15,16), afsS (SCO4425) (17,18), and absR1 (SCO6992) (19), encode regulatory proteins and were previously related to antibiotic regulation. An additional gene, SCO1839, encoding a putative transcriptional regulator with a helix-turn-helix motif, and two genes involved in morphological development, i.e., wblE (SCO5240; encodes an extracytoplasmic function [ECF] sigma factor [20,21]) and bdtA (SCO3328; encodes a putative transcription factor regulated by BldD and forms an operon with SCO3327 [22,23]), were also significantly downregulated.…”

“…To better characterize the pleiotropic effects exhibited by the ⌬abrC3 mutant, we conducted a global transcriptome analysis comparing the ⌬abrC3 mutant and the parental strain and showed that the low-level production of ACT observed in the abrC3 mutant was due to a general downregulation of transcription of the act gene cluster. Other regulatory genes previously associated with antibiotic production, such as the sIHF gene (SCO1480) (15,16), afsS (SCO4425) (17,18), and absR1 (SCO6992) (19), and with morphological development, for example, wblE (SCO5240) (20,21) and bdtA (SCO3328) (22,23), were also downregulated in this mutant. Furthermore, through chromatin immunoprecipitation with microarray technology (ChIP-chip) analyses, we demonstrated a direct regulation of act gene expression through AbrC3, and we provided independent verification with in vitro DNAbinding studies.…”

“…It is known that the biosynthetic RED genes are expressed early, so the existence of direct AbrC3 regulation of the promoter regions of redD or redZ cannot yet be excluded for the experimental conditions tested. If the RED cluster regulation by AbrC3 is indirect, this could be exerted through the regulatory cascade triggered by AfsS, which is one of the indirect AbrC3 targets (17,18), or by sIHF, which is downregulated in the ⌬abrC3 mutant and is able to bind to the redD and redZ promoters (15,16).…”