Guiding functions of the C-terminal domain of topoisomerase IIα advance mitotic chromosome assembly

Topoisomerase II (topo II) is one of the six proteins essential for mitotic chromatid reconstitution in vitro. It is not fully understood, however, mechanistically how this enzyme regulates this process. In an attempt to further refine the reconstitution assay, we have found that chromosomal binding of Xenopus laevis topo IIα is sensitive to buffer conditions and depends on its C-terminal domain (CTD). Enzymological assays using circular DNA substrates supports the idea that topo IIα first resolves inter-chromatid entanglements to drive individualization and then generates intra-chromatid entanglements to promote thickening. Importantly, only the latter process requires the CTD. By using frog egg extracts, we also show that the CTD contributes to proper formation of nucleosome-depleted chromatids by competing with a linker histone for non-nucleosomal DNA. Our results demonstrate that topo IIα utilizes its CTD to deliver the enzymatic core to crowded environments created during mitotic chromatid assembly, thereby fine-tuning this process.

DEVELOPMENT OF STUDENTS’ COGNITIVE ACTIVITY

It has been investigated different approaches to the definition of the concepts of “cognitive activity”, “cognitive functioning” and “cognitive autonomy”. Their comparisons have also been made. As a result we have found that cognitive function as a form of mental activity is aimed at cognition, perception and thinking of the learning subject. Cognitive activity is characterized as a personality trait that manifests itself in its relation to the process of cognition, readiness and desire for cognitive activity. It is proved that cognitive autonomy is a quality of the personality, which is inherent in the desire and ability without the help (independently) to acquire the necessary knowledge and skills, to solve tasks. The means, methods and conditions for improvement of students’ cognitive activity are determined i.e. a game as a way of activating cognitive functioning, project method, cognitive tasks, modeling, independent work, vocabulary work, web quest technology, project activity. It is concluded that all of them are focused on the students’ creative work, on the avoiding of the standard form of conducting classes and changing of thinking and participation of both the student and the teacher. It is noted the essential role of the teacher in the process of using such activities while working with students. The contemplative and guiding functions of the teacher in the learning process are distinguished. The importance of creating a work atmosphere comfortable for all participants is emphasized. Emphasis is placed on the fact that cognitive activity begins with activity, independence, initiative, desire to know more, go beyond what is already known. It is noted that the relationship between the student and the teacher has moved to the subject-subjective level, which enables the student to independently plan his/her activity, predict the results, be responsible for the final result of learning i.e. knowledge acquisition, comprehensive development and ability to work.

The extended Einstein–Maxwell-aether-axion model: Exact solutions for axionically controlled pp-wave aether modes

The extended Einstein–Maxwell-aether-axion model describes internal interactions inside the system, which contains gravitational, electromagnetic fields, the dynamic unit vector field describing the velocity of an aether, and the pseudoscalar field associated with the axionic dark matter. The specific feature of this model is that the axion field controls the dynamics of the aether through the guiding functions incorporated into Jacobson’s constitutive tensor. Depending on the state of the axion field, these guiding functions can control and switch on or switch off the influence of acceleration, shear, vorticity and expansion of the aether flow on the state of physical system as a whole. We obtain new exact solutions, which possess the pp-wave symmetry, and indicate them by the term pp-wave aether modes in contrast to the pure pp-waves, which cannot propagate in this field conglomerate. These exact solutions describe a specific dynamic state of the pseudoscalar field, which corresponds to one of the minima of the axion potential and switches off the influence of shear and expansion of the aether flow; the model does not impose restrictions on Jacobson’s coupling constants and on the axion mass. Properties of these new exact solutions are discussed.