Arnvig, K. B. | Search bioRxiv

bioRxiv2018

Dual RNAseq of human leprosy lesions identifies bacterial determinants linked to host immune response

To understand how the interaction between an intracellular bacterium and the host immune system contributes to outcome at the site of infection, we studied leprosy, a disease that forms a clinical spectrum, in which progressive infection by the intracellular bacterium Mycobacterium leprae is characterized by the production of type | IFNs and antibody production. We performed dual RNAseq on patient lesions, identifying a continuum of distinct bacterial states that are linked to the host immune response. The bacterial burden, represented by the fraction of bacterial transcripts, correlates with a host type | IFN gene signature, known to inhibit antimicrobial responses. Second, the bacterial transcriptional activity, defined by the bacterial mRNA/rRNA ratio, links bacterial heat shock proteins with the BAFF-BCMA host antibody response pathway. Our findings provide a platform for interrogation of host and pathogen transcriptomes at the site of infection, allowing insight into mechanisms of inflammation in human disease.

microbiology↗

bioRxiv2017

Cell-wall synthesis and ribosome maturation are co-regulated by an RNA switch in Mycobacterium tuberculosis

The success of Mycobacterium tuberculosis as a pathogen relies on the ability to switch between active growth and non-replicating persistence, associated with latent TB infection. Resuscitation promoting factors (Rpfs) are essential for the transition of M. tuberculosis to dormancy and for emergence from the non-replicating persistent state. But these enzymes are double-edged swords, as their ability to degrade the cell wall, is potentially lethal to the bacterium itself. Hence, Rpf expression is tightly regulated. We have identified a novel regulatory element in the 5 untranslated region (UTR) of rpfB. We demonstrate that this element is a transcriptionally regulated RNA switch/riboswitch candidate, which is restricted to pathogenic mycobacteria, suggesting a role in virulence. Moreover, we have used translation start site mapping to re-annotate the RpfB start codon and identified and validated a ribosome binding site that is likely to be targeted by an RpfB antisense RNA. Finally, we show that rpfB is co-transcribed with downstream genes, ksgA and ispE. ksgA encodes a universally conserved methyl transferase involved in ribosome maturation and ispE encodes an essential ATP-dependent kinase involved in cell wall synthesis. This arrangement implies co-regulation of resuscitation, cell wall synthesis and ribosome maturation via the RNA switch. We propose that deregulation of this switch, associated with cell wall synthesis and ribosome function, presents a new target for anti-tuberculosis drug development.\n\nImportanceThis work describes the identification and characterisation of a novel regulatory RNA element/attenuator that controls cell wall synthesis and ribosome function in Mycobacterium tuberculosis, the causative agent of human tuberculosis (TB). By switching between two different conformations, this RNA switch can either enable or inhibit transcription of a tri-cistronic mRNA that encodes a cell-wall remodelling enzyme crucial for activation of latent TB, an RNA methytransferase that is important for ribosome function and a protein kinase essential for early steps in cell wall synthesis. This RNA switch is only present in a subset of pathogenic mycobacteria, and by regulating the expression of three genes associated with classical antimicrobial targets we believe that it offers a novel important target for future anti-tuberculosis drugs.

molecular biology↗