Distinct regulation across the transcription cycle drives mitotic transcriptional silencing
In most organisms, as cells enter mitosis, transcription is globally silenced. While individual studies have shown that each stage of the transcription cycle can be modulated during mitosis, how initiation, elongation, and termination are temporally and kinetically regulated to ensure transcriptional silencing remains unclear. Here, we combine real-time quantitative imaging of ongoing…
During the progression of cells into mitosis, global transcriptional silencing occurs across most organisms. Although previous studies have observed that various stages of transcription can be modulated during mitosis, the mechanisms regulating the initiation, elongation, and termination of transcription during this process remain unclear.
To address this knowledge gap, researchers combined real-time quantitative imaging of ongoing transcription in early Drosophila embryos with mathematical modeling to systematically examine how transcriptional kinetics change as cells enter mitosis.
The study revealed that transcription initiation experiences a gradual repression beginning in prophase, while elongation rates remain unchanged. After the nuclear envelope breaks down, an abrupt mechanism causes the premature termination of elongating RNA. This termination is at least partially driven by the SNF-helicase-like protein Transcription Termination factor 2 / Lodestar (TTF2/Lds).
The findings provide a quantitative framework for understanding how transcription is regulated across the cell cycle. The research demonstrates that mitotic repression emerges from a combination of multiple processes, each with distinct dynamics, working together to ensure the precise shutdown of gene expression during mitosis.
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