Condensins I and II are essential genome maintenance enzymes responsible for condensing the chromatin during mitosis in preparation for cell division. As chromatin is condensed, transcription is gradually shut off. It is not known, however, whether compaction prevents transcription, or vice versa and if the processes are regulated separately. Continuous ribosome production is important for survival of dividing cells and in particular survival of cancer cells. Transcription of ribosomal DNA is therefore shut off later in mitosis than the rest of the genome. In yeast, shut off occurs as late as anaphase and in higher organisms in late prophase to early prometaphase. In this project, I focus on the highly transcribed ribosomal DNA to investigate the role of condensins in transcription shutoff and re-initiation. Conditional Tet-OFF knockouts in combination with epitope and fluorescently tagged condensin I and II subunits are used to perform experiments in chicken DT40 cells. Using this model system, I have found that condensin I, but not condensin II, is highly enriched at the ribosomal DNA from prometaphase till the end of mitosis. Complementing that result, condensin I, but not condensin II, appears to be required for re-initiation of rDNA transcription at the end of mitosis. The conditional knockout methods applied so far for condensin analysis rely on condensin depletion spanning several cell cycles. A caveat with the chicken DT40 Tet-OFF system is that is depletes protein over a cell cycle. Therefore, we’ve engineered an ultra-rapid system for depletion of condensins in human cells using the Auxin-degron approach which allows complete depletion in 15-30 min. Preliminary experiments with these cells suggest that DNA bridging and cytokinesis failure are primary phenotypes derived from the first condensin deficient mitosis. This study combines a plethora of molecular biology tools to pinpoint the functions of the condensin complexes.