Identification and characterization of a direct activator of a gene transfer agent

Paul C M Fogg

doi:10.1038/s41467-019-08526-1

Abstract

Gene transfer agents (GTAs) are thought to be ancient bacteriophages that have been co-opted into serving their host and can now transfer any gene between bacteria. Production of GTAs is controlled by several global regulators through unclear mechanisms. In Rhodobacter capsulatus, gene rcc01865 encodes a putative regulatory protein that is essential for GTA production. Here, I show that rcc01865 (hereafter gafA) encodes a transcriptional regulator that binds to the GTA promoter to initiate production of structural and DNA packaging components. Expression of gafA is in turn controlled by the pleiotropic regulator protein CtrA and the quorum-sensing regulator GtaR. GafA and CtrA work together to promote GTA maturation and eventual release through cell lysis. Identification of GafA as a direct GTA regulator allows the first integrated regulatory model to be proposed and paves the way for discovery of GTAs in other species that possess gafA homologues.

Highlights

Gene transfer agents (GTAs) are thought to be ancient bacteriophages that have been co-opted into serving their host and can transfer any gene between bacteria
Host bacterial DNA is packaged into a significant proportion of phage particles instead of the phage genome; the host DNA can be randomly selected (GT phages) or it can be from a large hypermobile region (LT phages)
All RcGTA genes are upregulated in an RcGTA hyperproducer

Summary

Introduction

Gene transfer agents (GTAs) are thought to be ancient bacteriophages that have been co-opted into serving their host and can transfer any gene between bacteria. CtrA and GafA are both required for optimal RcGTA expression, packaging of DNA and release of infective particles. Similar to gafA, deletion of ctrA prevents any detectable RcGTA gene transfer or production of the RcGTA capsid protein[14].

Results

Conclusion