AUTHOR=Afzal Muhammad , Shafeeq Sulman , Kuipers Oscar P. 

TITLE=NADH-Mediated Gene Expression in Streptococcus pneumoniae and Role of Rex as a Transcriptional Repressor of the Rex-Regulon

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01300

DOI=10.3389/fmicb.2018.01300

ISSN=1664-302X

ABSTRACT=<p>Nicotinamide adenine dinucleotides (NAD(H)) play a vital role in various biological processes, including keeping the cellular redox balance. In this study, we investigate the regulatory responses of <italic>Streptococcus pneumoniae</italic> D39 to NADH and characterize the role of the Rex protein as a transcriptional repressor of the <italic>gapN, fba, pncB, adhB2, gap</italic>, and <italic>adhE</italic> genes. Transcriptomic analysis was used to observe the response of <italic>S. pneumoniae</italic> D39 to NADH. Our microarray studies revealed elevated expression of various genes/operons involved in transport and biosynthesis of niacin (<italic>gapN, fba, pncB, adhB2, gap</italic>, and <italic>adhE</italic>). Promoter <italic>lacZ</italic>-fusion assays and microarray studies with the <italic>rex</italic> mutant revealed the role of Rex as a transcriptional repressor of <italic>gapN, fba, pncB, adhB2, gap</italic>, and <italic>adhE</italic> involved in niacin uptake and biosynthesis, in the presence of NADH. We predict the operator site (5′-TTGTKAWAAWWTTCACAA-3′) of Rex in the regulatory regions of Rex-regulated genes that was subsequently validated by promoter mutational experiments.</p>