FIG. 1.

Assay for Ty1 activity. (A) The yeast strain LV47 was transformed with two plasmids: pGPol(−)hisAI, a TRP1-based derivative of pGTy1-H3mHIS3AI with an active-site mutation in RT (RT*), and pJEFWTneo, a wild-type URA3-based plasmid or mutant derivatives of this plasmid with deletions or active-site mutations in the IN gene (IN*). (B) On galactose induction, VLPs are formed and assembled in the cytoplasm. Two molecules of genomic RNA are packaged into the VLPs. (C) The genomic Ty1 RNA is reverse transcribed by the IN/RT complex. The full-length double-stranded DNA which is synthesized forms a PIC. (D) The PIC is then transported into the nucleus. IN insert the Ty1 DNA into the host genome (transposition).