Selectivity and errors in bacteriophage DNA packaging – SelectVir

The goal of the project SelectVir is to characterize the mechanisms used by bacterial viruses (phages) to package selectively their DNA in preformed viral procapsids and to assess the mechanisms by which errors of the phage machinery lead to packaging of bacterial DNA (transduction).
The phage SPP1 protein TerS recognizes specifically a pac sequence to initiate unidirectional packaging of its DNA into viral procapsids. Mutations in TerS (TerS*) lead to hyper-transduction showing that phages can rapidly evolve to become highly efficient horizontal gene transfer agents that disseminate, for example, antibiotic resistance, pathogenicity factors and other genetic features within bacterial communities.
In this research project we will investigate the sequence binding specificity of SPP1 TerS and of TerS* in vivo, and will characterize such protein-DNA interaction in vitro using purified proteins and their target sequences. Biochemical and structural studies of the nucleoprotein complexes assembled sequentially at pac will aim to understand the molecular events necessary to initiate packaging into viral procapsids.
Phage SPP1 genome replication effectors and procapsids are found in a membrane-less viral DNA compartment within the host bacterial cytoplasm. This finding prompts imaging the formation of DNA packaging centers during wild type and TerS* mutants infection in order to correlate their position relative to phage and bacterial DNAs.
This research work aims to uncover the molecular and cellular mechanisms leading to selective phage DNA packaging and to phage transduction of host genetic information.