Functions of Archaeal Nucleoid Proteins: Archaeal Silencers are Still Missing

Abstract

It is well known that horizontally transferred genes (HTGs) contribute to the adaptation of archaea to their living environment. Archaea have acquired HTGs not only from other archaea but also from bacteria. HTGs should be integrated into the host archaeal transcriptional networks to become functional. In bacteria, the nucleoid proteins, such as H-NS and Lsr2, are well known as the major factors to enhance horizontal transfer of foreign DNAs into the bacterial cells by silencing the expression of HTGs which permit bacteria to safely acquire the HTGs and give time to modify the regulatory elements and promoters of HTGs and to integrate the HTGs into host transcriptional networks. In archaea, although those factors have not been identified, the importance of silencers would be the same. Interestingly, there is a protein which has highly similar characteristics with H-NS in the hyperthermophilic archaeon Thermococcus kodakarensis. In this chapter, we summarize the known biological importance of the nucleoid proteins and histones in archaea and discuss the possible role of the archaeal nucleoid proteins in horizontal gene transfer in archaeal cells.