Global spread of multidrug-resistant M. tuberculosis (Mtb) strains and
emergence of extensively drug-resistant tuberculosis (TB) call for
innovative approaches for treating TB. As conventional first- and
second-line anti-TB drugs are gradually rendered less useful due to
drug resistance,1 and the number of drug candidates in the anti-TB
pipeline is low,2 novel targets and agents inhibiting them need to be
explored. Bacterial primase DnaG, a DNA-dependent RNA polymerase
that synthesizes oligonucleotide primers during DNA replication,
has been known for several decades to be essential for both
chromosomal DNA replication and cell division.3–6 DnaG is conserved
in bacteria and is distinct from eukaryotic and archaeal primases.7 In
addition, the catalytic TOPRIM (topoisomerase-primase) domain of
DnaG shares a structural fold with DNA gyrase, a target of the
clinically useful fluoroquinolone antibiotics.8 Therefore, DnaG is an
attractive potential target for discovery and development of novel
antibacterial agents. The requirements of radioactivity as a detection
method and accessory DNA replication factors to boost primase
activity in traditional in vitro primase activity assays have impeded
facile identification and characterization of DnaG inhibitors, and, until
recently, no potent (low-μM or better) inhibitors of DnaG were
reported.