G0/G1 cell cycle arrest in the brain of Sarcophaga crassipalpis during pupal diapause and the expression pattern of the cell cycle regulator, proliferating cell nuclear antigen.

During pupal diapause in the flesh fly, Sarcophaga crassipalpis, the cells of the brain are arrested in the G0/G1 phase of the cell cycle. When diapause is terminated with a topical application of hexane, cell cycling is evident within 12 hours. Four G1 and S phase regulatory genes were examined by Northern blot analysis to evaluate their expression patterns in relation to this cell cycle arrest. A distinction between diapausing and nondiapausing individuals was noted only for Proliferating Cell Nuclear Antigen (PCNA). PCNA was highly expressed after diapause was terminated but not during diapause. In contrast, cyclin E, p21, and p53 were expressed equally at all times. In situ hybridization using PCNA probes further indicated a correlation between PCNA transcription (expression) in the brain and cell cycling. Our evidence thus suggests a potential role for PCNA as an important regulator of cell cycle arrest during diapause.