FORMATION OF BACTERIOPHAGE-MS2 INFECTIOUS UNITS IN A CELL-FREE TRANSLATION SYSTEM

We show that a simple cell-free translation system from Escherichia co li, programmed with phage MS2 RNA, is able to infect F+ E. coli cells, The plaques appearing on the E. coli host strain are morphologically indistinguishable from those derived from normal phage MS2 infection, This effect is strictly translation-dependent, since an incomplete tra nslation system or the system inhibited by antibiotics leads to no inf ection, The cell-free based infection is maximal under conditions favo uring the highest synthesis of maturation protein (one of the four pha ge-encoded proteins), The infection is abolished when RNase A or tryps in treatment is included before addition of cells, Similarly, due to R NA and maturation protein degradation, the continued incubation of the translation mixture under protein synthesis conditions significantly decreases infectivity, These findings suggest the formation of 'minima l infectious units', simple complexes of MS2 RNA and maturation protei n, Here we describe the first example of bacteriophage infectious unit formation directly performed in a cell-free translation system, A pos sible application of this phenomenon might be the construction of newl y designed RNA vector delivery systems and, moreover, could be an appr oach for molecular evolution studies.