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Xenopus Tropicalis Egg Extracts Provide Insight Into Scaling Of The Mitotic Spindle, Thomas J. Maresca, M. D. Blower, K. S. Brown, T. C. Grammer, R. M. Harland, R. Heald
Xenopus Tropicalis Egg Extracts Provide Insight Into Scaling Of The Mitotic Spindle, Thomas J. Maresca, M. D. Blower, K. S. Brown, T. C. Grammer, R. M. Harland, R. Heald
Thomas J. Maresca
The African clawed frog Xenopus laevis has been instrumental to investigations of both development and cell biology, but the utility of this model organism for genetic and proteomic studies is limited by its long generation time and unsequenced pseudotetraploid genome. Xenopus tropicalis, which is a small, faster-breeding relative of X. laevis, has recently been adopted for research in developmental genetics and functional genomics, and has been chosen for genome sequencing. We show that X. tropicalis egg extracts reconstitute the fundamental cell cycle events of nuclear formation and bipolar spindle assembly around exogenously added sperm nuclei. Interestingly, X. tropicalis spindles were …
Micromanipulation Studies Of Chromatin Fibers In Xenopus Egg Extracts Reveal Atp-Dependent Nucleosome Assembly Dynamics, Thomas J. Maresca, J. Yan, D. Skoko, R. Heald, J. F. Marko
Micromanipulation Studies Of Chromatin Fibers In Xenopus Egg Extracts Reveal Atp-Dependent Nucleosome Assembly Dynamics, Thomas J. Maresca, J. Yan, D. Skoko, R. Heald, J. F. Marko
Thomas J. Maresca
We have studied assembly of chromatin using Xenopus egg extracts and single DNA molecules held at constant tension by using magnetic tweezers. In the absence of ATP, interphase extracts were able to assemble chromatin against DNA tensions of up to 3.5 piconewtons (pN). We observed force-induced disassembly and opening–closing fluctuations, indicating our experiments were in mechanochemical equilibrium. Roughly 50-nm (150-base pair) lengthening events dominated force-driven disassembly, suggesting that the assembled fibers are chiefly composed of nucleosomes. The ATP-depleted reaction was able to do mechanical work of 27 kcal/mol per 50 nm step, which provides an estimate of the free energy …