| Popis: |
This chapter is centered on studies of IS911 as a model system for studying the large IS3 group. The present understanding of the steps in IS911 transposition is shown. However, important insights and some intriguing differences have been revealed from other members and these are described where appropriate. Different roles for OrfA have been proposed for different IS3 family members: stimulation of transposon circle integration for IS911; inhibition of transposition for IS3; and repression of transposase expression for IS2. Mutation of the terminal dinucleotide at one or both ends of the junction significantly reduces cleavage of the mutated end in vivo and in vitro, and the same single- and double-end mutations strongly reduce the transposition frequency in vivo. In conclusion, by IS2, IS3, IS150, and IS911 probably share the same transposition pathway but may be differently regulated by OrfA and possibly by OrfB. Many transposable elements are separated from their flanking donor DNA prior to insertion into a target site. This behavior, termed cut-and-paste, requires processing of both strands at each end of the element. |
