Structure specific ds&2.urule;ss-RNase activity in the extreme halophile Halobacterium salinarium

A ds/ss-RNA processing activity involved in antisense-RNA mediated gene regulation in the extremely halophilic archaebacterium Halobacterium salinarium was investigated in vivo. H.salinarium cells were transformed with DNA encoding an RNA species complementary to a part of the major lytic transcript, termed T4, of the H.salinarium phage phi H. The transformants transcribing this construct, when infected by phage were able to process T4 in a similar way to the processing of the lytic transcript denoted T1, in the natural sense-antisense system. Processing of T4 was not observed under normal phage growth on wild-type cells. Thus the antisense-RNA mediated processing activity earlier reported is dependent on the presence of an RNA duplex and is not sequence specific.