Reporter gene assay in yeast cells pAC99 reporter plasmids were transformed into yeast strain Y349 using the LiOAc/ssDNA/PEG method [27] . For each experiment three transformants cultivated under the same conditions were assayed. Cells were disrupted by vortexing with acid washed glass beads (Sigma) at 4uC for 30 minutes. Cell debris was removed by centrifugation and reporter enzyme assays carried out as described [23] . Termination-reinitiation efficiency was calculated as the ratio of firefly luciferase activity to b-galactosidase activity relative to that of constructs in which the open reading frames were fused in frame.