Kn. Johnson et al., Reverse transcription of a naturally occurring nonretroviral RNA produces a precise deletion in the majority of its cDNA products, IUBMB LIFE, 49(3), 2000, pp. 223-227
A precise, reproducible deletion made during in vitro reverse transcription
of RNA2 from the icosahedral positive-stranded Helicoverpa armigera stunt
virus (Tetraviridae) is described. The deletion, located between two hexame
r repeats, is a 50-base sequence that includes one copy of the hexamer repe
at. Only the Moloney murine leukemia virus reverse transcriptase and its de
rivative Superscript I, carrying a deletion of the carboxy-terminal RNase H
region, showed this response, indicating a template-switching mechanism di
fferent from one proposed that involves a RNase H-dependent strand transfer
, Superscript II, however, which carries point mutations to reduce RNase H
activity, does not cause a deletion. A possible mechanism involves the enzy
me pausing at the 3' side of a stem-loop structure and the 3' end of the na
scent DNA strand separating from the template and reannealing to the upstre
am hexamer repeat.