Mitotic Transcription and Waves of Gene Reactivation During Mitotic Exit

The genome is thought to be transcriptionally silent during mitosis. Technical limitations have prevented the sensitive mapping of mitotic transcription and transcription reactivation during mitotic exit, and thus the networks by which transcriptome dynamics govern the generation of daughter cells have been unclear. We used 5-ethynyluridine to pulse-label intact transcripts during mitosis and mitotic exit and find that the first round of transcription activates genes that are involved in macromolecular synthesis, rather than cell identity. Many interphase genes exhibit residual transcription in mitosis, as confirmed by different methods of assessment, and a subset of genes are more highly transcribed in mitosis than in interphase. We suggest that mitotic transcription may serve an epigenetic function in restoring proper transcription patterns during mitotic exit. Overall design: All samples in triplicates A, B, and C; experimental time points = 0, 40, 80, 105, 165, 300, EU; No label control = NoEU. Samples in triplicates D, E, F: mitotic, async; samples in duplicate: NoEU D, E.