General Interests
Ribosomes are protein manufacturers that are essential for all cells and viruses. Our lab applies genetic, structural and biochemical principles to understand how ribosome composition and associations, antibiotics and stressors affect the translation of genetic codes and, in turn, give rise to phenotypic variations and differential manifestations of infection. Our focus spans fundamental basic biology and extends to understanding bacterial physiology and human and plant diseases.
Research Areas/Projects
Ribosome hibernation
The bacterial 100S ribosome (dimer of 70S complexes) is important for pathogenesis, translational repression, starvation responses, and ribosome turnover. Our goal is to establish a mechanistic understanding of the biogenesis and function of the 100S ribosome in translational silencing and staphylococcal pathogenesis. This project focuses on the following unexplored questions: What factors control the constitutive production of the 100S ribosome in S. aureus? Why are only specific mRNAs translationally repressed during ribosome hibernation? How is hibernation beneficial to ribosome stability? How is ribosome turnover linked to successful host colonization?
RNA degradation pathways
S. aureus ribosomes lacking hibernation-promoting factor (Hpf) are rapidly degraded by the 3’-5’ exonuclease RNase R and other hitherto unknown ribonucleases. We isolated an additional ribonuclease mutant that rescues the loss of ribosomes. This project aims to determine the mechanisms by which Hpf protects ribosomes from ribonucleolytic degradation.
Multidrug resistant ribosome
Macrolides, lincosamides and streptogramins (MLS) are structurally distinct and broad-spectrum antibiotics that inhibit protein biosynthesis by binding to the 50S large subunit of bacterial ribosome.The efficacy of MLS has rapidly eroded due to the widespread dissemination of the Erm RNA methyltransferases that catalyze the transfer of two methyl groups to a conserved adenine nucleotide (m6A2058) in the 23S rRNA of the 50S subunit. This dimethylation sterically hinders the binding of all MLS antibiotics that share the overlapping A2058, in addition to abrogating the MLS resistant bacteria from host immune recognition. Our studies seek to addresses several unresolved questions: How is the expression of erm regulated under antibiotic selection? How does Erm find its target? What are the consequences of ribosome methylation? How do the next-generation antibiotics recognize the methylated ribosome?
Glutamate metabolism
While Hpf homologs are only known to target ribosomes, we recently found that Hpf directly interacts with an extra-ribosomal protein (YwlG). YwlG is a virulence factor of unknown biological activity. Sequestration of Hpf by YwlG reduces the formation of 100S ribosomes. Conversely, Hpf suppresses YwlG-dependent NAD-specific glutamate dehydrogenase (GDH) activity. YwlG adopts a hexameric structure with two stacked trimers but by itself does not exhibit GDH activity. This project will investigate the biochemical and structural features of YwlG-Hpf interactions, as well as identify additional interactional partners of YwlG.