Recognition of template RNA by Qβ polymerase: Sequence at the 3′-terminus of Qβ 6S RNA

Abstract

The major 3′-terminal sequences of Qβ 6S RNA have been determined by a combination of 3′-terminal labeling with 3H via the periodate-borohydride procedure, labeling of specific bases using 14C-labeled triphosphates and by ribonuclease T 1 digestion. The predominant sequence was GpCpCpA OH with lesser amounts of GpCpC OH and GpCpCpG OH. Since the sole 5′-terminal base of 6S RNA is G, these results provide another example of the ability of Qβ polymerase to add a noncomplementary adenosine to the 3′-end and the first example of an ability to add a guanosine. Thus, all major sequences found may be considered derivatives of the sequence GpCpC OH. This sequence differs significantly from those of other Qβ polymerase templates studied thus far, and thus reaffirms the requirement for additional internal structural features by which Qβ polymerase recognizes its templates.