Following exit from mitosis, RNA Pol II is required for reestablishing 3D genome folding by loading cohesin complexes onto DNA.

Mammalian chromosomes are three-dimensional entities shaped by converging and opposing forces. Mitotic cell division induces drastic chromosome condensation, but following reentry into the G1 cell cycle phase, condensed chromosomes unwind to reestablish interphase organization. Here, we use a cell line allowing auxin-mediated degradation of RNA polymerase II to test its role in this transition. In situ Hi-C showed that RNAPII is required for compartment and loop formation following mitosis. RNAPs often counteract loop extrusion and, in their absence, longer and more prominent loops arise. Evidence from chromatin fractionation, super-resolution imaging and in silico modeling attribute these effects to RNAPII-mediated cohesin loading at active promoters upon reentry into G1. Our findings reconcile the role of RNAPII in gene expression with that in chromatin architecture.

Braids composed of two interwoven polymer chains exhibit a "buckling" transition whose origin has been explained through the onset of plectonemic structures. Here we study, by a combination of simulation and analytics, the dynamics of plectoneme formation and their statistics in steady state. The introduction of an order parameter -the plectonemic fraction -allows us to map out the phase boundary between the straight braid phase and the plectonemic one. We then monitor the formation and the growth of plectonemes, observing events typical of phase separation kinetics for liquid-gas systems (fusion, fission, 1D Ostwald ripening), but also of DNA supercoiling dynamics (plectonemic hopping). Finally, we propose a stochastic field theory for the coupled dynamics of twist and local writhe which explains the phenomenology found with Brownian dynamics simulations as well as the power laws underlying the coarsening of plectonemes. arXiv:1903.06430v1 [cond-mat.soft]

This work sets out the planning phases adopted for the first time to put together a manual on injury and accident prevention in the use of farm tractors. The goal is to convey information more effectively than at present, while taking the end users' opinions into consideration. The manual was devised, created, and tested based on a human-centred design (HCD) process, which identified the operators' requirements using a participatory ergonomics (PE) strategy. The main topics of the manual were outlined by engaging the users in a qualitative research activity (i.e., focus groups and workshops with final users), and the contents were prioritized and labelled by way of a noun prioritization activity. The users were involved right up to the choice of graphics and print layout in order to orient the publication to the farming context. The research activity highlighted a divergence between the operators' requirements and the topics currently dealt with in the sector publications. The project resulted in the publication of the "Safe Tractor" manual, which features some innovations. The experience highlighted the need to adopt HCD processes to create innovative editorial products, which can help speed up the dissemination of safety culture in the primary sector.