[Phase-specific elements of the regulatory zone of the Drosophila melanogaster string gene]

The phases of the reporter gene expression controlled by different fragments of the string (stg) gene regulatory region were determined in Drosophila neuroblasts by detection of beta-galactosidase activity and radioautography. In the D10 and D22 lines carrying the constructs pstg beta-E4.9 and pstg beta-E5.3, respectively, the reporter gene activity was detected in the G1 phase of the cell cycle. In the D12 and D20 lines (pstg beta-E6.4 and pstg beta-E2.6), no periodic expression was observed. The regulatory regions of the stg from lines D10 and D22 and that of Drosophila gene cyclin D shared consensus aagaactttg, which was also expressed in the G1 phase. The phase-specific expression of the cell-cycle genes was compared in a model for the mitotic-wave cells of eye imaginal disk and neuroblasts of the nerve ganglia.