Niacin-mediated Gene Expression and Role of NiaR as a Transcriptional Repressor ofniaX, nadC, andpnuCinStreptococcus pneumoniae.
NAD (Nicotinamide Adenine Dinucleotide) biosynthesis is vital for bacterial physiology and plays an important role in cellular metabolism. A naturally occurring vitamin B complex, niacin (nicotinic acid), is a precursor of coenzymes NAD and NADP. Here, we study the impact of niacin on global gene expression ofStreptococcus pneumoniaeD39 and elucidate the role of NiaR as a transcriptional regulator ofniaX, nadC, andpnuC. Transcriptome comparison of the D39 wild-type grown in chemically defined medium (CDM) with 0 to 10 mM niacin revealed elevated expression of various genes, includingniaX, nadC, pnuC, fba, rex, gapN, pncB, gap, adhE, andadhB2that are putatively involved in the transport and utilization of niacin. Niacin-dependent expression of these genes is confirmed by promoterlacZ-fusion studies. Moreover, the role of transcriptional regulator NiaR in the regulation of these genes is explored by DNA microarray analysis. Our transcriptomic comparison of D39 ΔniaRto D39 wild-type revealed that the transcriptional regulator NiaR acts as a transcriptional repressor ofniaX, pnuC, andnadC. NiaR-dependent regulation ofniaX, nadC, andpnuCis further confirmed by promoterlacZ-fusion studies. The putative operator site of NiaR (5'-TACWRGTGTMTWKACASYTRWAW-3') in the promoter regions ofniaX, nadC, andpnuCis predicted and further confirmed by promoter mutational experiments.
Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of GroningenGroningen, Netherlands; Department of Bioinformatics and Biotechnology, Government College UniversityFaisalabad, Pakistan.
Muhammad
M
Afzal
Department of Molecular Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen Groningen, Netherlands.
Oscar P
OP
Kuipers
Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet Stockholm, Sweden.
Sulman
S
Shafeeq
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D017930:Genes, Reporter; D046228:Microarray Analysis; D009525:Niacin / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000235:genetics* / Q000378:metabolism*; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics
D001426:Bacterial Proteins; D012097:Repressor Proteins; D009525:Niacin; D001616:beta-Galactosidase
NiaR; Pneumococcus; nadC; niaX; niacin; pnuC