9.A.53 The Crenarchaeal System for Exchange of DNA (Ced) Family 

Intercellular transfer of DNA occurs universally, in all domains of life. Upon UV-light treatment, cells of the crenarchaeal genus Sulfolobus express Ups pili, which initiate cell aggregate formation. Within these aggregates, chromosomal DNA, which is used for the repair of DNA double-strand breaks, is exchanged.  van Wolferen et al. 2016 identify saci_0568 (CedA; Q4JB69) and saci_0748 (CedB; Q4JAQ5), two genes from Sulfolobus acidocaldarius that are highly induced upon UV treatment, encoding a transmembrane protein and a membrane-bound VirB4/HerA homolog, respectively. DNA transfer assays showed that both proteins are essential for DNA transfer between Sulfolobus cells and act downstream of the Ups pilus system. The system is involved in the import of DNA rather than the export. Thus, Saci_0568 and Saci_0748 are part of a previously unidentified DNA importer. The cedA gene is flanked by two genes, CedA1 and CedA2 that form a complex with CedA and CedB in the membrane (van Wolferen et al. 2016). This transport system occurs widely among the Crenarchaeota.