Micromechanics of chromatin and chromosomes

2003 ◽  
Vol 81 (3) ◽  
pp. 209-220 ◽  
Author(s):  
John F Marko ◽  
Michael G Poirier

The enzymes that transcribe, recombine, package, and duplicate the eukaryotic genome all are highly processive and capable of generating large forces. Understanding chromosome function therefore will require analysis of mechanics as well as biochemistry. Here we review development of new biophysical-biochemical techniques for studying the mechanical properties of isolated chromatin fibers and chromosomes. We also discuss microscopy-based experiments on cells that visualize chromosome structure and dynamics. Experiments on chromatin tell us about its flexibility and fluctuation, as well as quantifying the forces generated during chromatin assembly. Experiments on whole chromosomes provide insight into the higher-order organization of chromatin; for example, recent experiments have shown that the mitotic chromosome is held together by isolated chromatin-chromatin links and not a large, mechanically contiguous non-DNA "scaffold".Key words: DNA struture, chromatin, chromosomes, mitosis.

Author(s):  
David A. Agard ◽  
Jason R. Swedlow ◽  
Yasushi Hiraoka ◽  
Michael R. Paddy ◽  
John W. Sedat

Cellular DNA is packaged into chromosomes through complex processes whereby the DNA becomes compacted up to 10,000-fold by assembly into higher-order structures. In spite of many decades of intense study, the details of this process are not known. In addition, there is little information describing the dynamics of these higher-order structures during DNA replication, transcription, and mitosis. The goal of our laboratory is to use state-of-the-art 3-D imaging methods to understand how DNA is arranged into chromosomes and how chromosomes are spatially and temporally organized in the nucleus.


Author(s):  
Jason R. Swedlow ◽  
Yasushi Hiraoka ◽  
Michael R. Paddy ◽  
John W. Sedat ◽  
David A. Agard

Cellular DNA is packaged into chromosomes through complex processes whereby the DNA becomes compacted up to 10,000-fold by assembly into higher-order structures. In spite of many decades of intense study, the details of this process are not known. In addition, there is little information describing the dynamics of these higher-order structures during DNA replication, transcription, and mitosis. The goal of our laboratory is to use state-of-the-art 3-D imaging methods to understand how DNA is arranged into chromosomes and how chromosomes are spatially and temporally organized in the nucleus.Towards this end, we have developed a fluorescence microscope workstation optimized for collecting three-dimensional multi-wavelength data from fixed and living specimens. The multiplewavelength capability of this system allows us to simultaneously examine the spatial relationships of different chromosomal components in 3-D. Fixed samples can be labelled with up to three different fluorophore-conjugated antibodies and a fluorescent DNA binding dye, DAPI. Three-dimensional multi-wavelength data collection proceeds by sequentially recording images of each color, changing the focus, and then repeating the process as many times as necessary.


eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Oliver Crawley ◽  
Consuelo Barroso ◽  
Sarah Testori ◽  
Nuria Ferrandiz ◽  
Nicola Silva ◽  
...  

Wapl induces cohesin dissociation from DNA throughout the mitotic cell cycle, modulating sister chromatid cohesion and higher-order chromatin structure. Cohesin complexes containing meiosis-specific kleisin subunits govern most aspects of meiotic chromosome function, but whether Wapl regulates these complexes remains unknown. We show that during C. elegans oogenesis WAPL-1 antagonizes binding of cohesin containing COH-3/4 kleisins, but not REC-8, demonstrating that sensitivity to WAPL-1 is dictated by kleisin identity. By restricting the amount of chromosome-associated COH-3/4 cohesin, WAPL-1 controls chromosome structure throughout meiotic prophase. In the absence of REC-8, WAPL-1 inhibits COH-3/4-mediated cohesion, which requires crossover-fated events formed during meiotic recombination. Thus, WAPL-1 promotes functional specialization of meiotic cohesin: WAPL-1-sensitive COH-3/4 complexes modulate higher-order chromosome structure, while WAPL-1-refractory REC-8 complexes provide stable cohesion. Surprisingly, a WAPL-1-independent mechanism removes cohesin before metaphase I. Our studies provide insight into how meiosis-specific cohesin complexes are regulated to ensure formation of euploid gametes.


2006 ◽  
Vol 73 ◽  
pp. 109-119 ◽  
Author(s):  
Chris Stockdale ◽  
Michael Bruno ◽  
Helder Ferreira ◽  
Elisa Garcia-Wilson ◽  
Nicola Wiechens ◽  
...  

In the 30 years since the discovery of the nucleosome, our picture of it has come into sharp focus. The recent high-resolution structures have provided a wealth of insight into the function of the nucleosome, but they are inherently static. Our current knowledge of how nucleosomes can be reconfigured dynamically is at a much earlier stage. Here, recent advances in the understanding of chromatin structure and dynamics are highlighted. The ways in which different modes of nucleosome reconfiguration are likely to influence each other are discussed, and some of the factors likely to regulate the dynamic properties of nucleosomes are considered.


2020 ◽  
pp. 122-124
Author(s):  
Зиля Ахмерова

Аннотация. Деятельностный подход к организации учебных занятий при профессиональной подготовке специалистов представляет технологию индивидуализированного обучения. В данной статье проведен экскурс по проблеме деятельности. Деятельность рассматривается как способ участия индивида в преобразовании существующей действительности, как метод познания, как условие проявления и развития личности, как условие конструирования отношений между людьми. Функции деятельности непосредственно связаны не только с проектной деятельностью, но и с развитием личности. Поэтому деятельностная организация процесса проектирования как метода развития личности является актуальной. Кроме этого отмечается, что роль преподавателя в ходе осуществления личностно-деятельностного подхода заключается в умелой организации образовательно- профессиональной среды. Ключевые слова: деятельность, личность, учебная деятельность, проектная деятельность, личностно-деятельностные технологии. Аннотация. Адистерди кесиптик даярдоо учурунда окуу сабактарын уюштуруунун ишмердик ыкмасы жеке инсанга багытталган окутуу технологиясы болуп эсептелет. Бул макалада ишмердик маселеси боюнча экскурс жүргүзүлгөн. Ишмердүүлүк учурдагы чындыкты кайра өзгөртүп түзүүдөгү индивиддин катышуу жолу катары, таануу методу катары, инсандын өзүн көрсөтүүсүнүн жана өнүгүүсүнүн шарты катары, адамдар ортосунда мамиле түзүү ыкмасы катары каралат. Ишмердүүлүктүн функциялары долбоордук иштер менен гана эмес, инсандын өнүгүүсү менен да түздөн-түз байланыштуу. Ошондуктан инсанды өнүктүрүүнүн ыкмасы катары долбоорлоо процессинин ишмердик уюштурулушу актуалдуу. Мындан тышкары, жеке инсанга багытталган – ишмердик ыкмасын ишке ашыруудагы окутуучунун ролу билим берүүчүлүк-кесиптик чөйрөнү эптүү уюштуруу экендиги белгиленет. Түйүндүү сөздөр: ишмердүүлүк, инсан, окуу иши, долбоордук иш, жеке инсанга багытталган – ишмердик технологиялар. Annotation. The activity approach to organization of study in the profession- al training of specialists represents the individualized training technique. This article makes the insight into the activity issue. The activity is considered as a way of person’s participation in transformation of existing reality, as a way of learning, as a condition for personality demonstration and development, as a condition for building relations be- tween people. The functions of the activity are immediately associated with not only de- signing activity but with development of the personality. That is why activity organization of the designing process as a way of personality development is relevant. However, in the modern education, the personal and activity approach is to be com- bined with other approaches of the collective activity based on self-government and competitiveness. Key words: activity, personality, studies, designing activity, personal and activity techniques


Nanophotonics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 3881-3887
Author(s):  
Ankit Arora ◽  
Pramoda K. Nayak ◽  
Tejendra Dixit ◽  
Kolla Lakshmi Ganapathi ◽  
Ananth Krishnan ◽  
...  

AbstractWe report on multiple excitonic resonances in bilayer tungsten diselenide (BL-WSe2) stacked at different angles and demonstrate the use of the stacking angle to control the occurrence of these excitations. BL-WSe2 with different stacking angles were fabricated by stacking chemical vapour deposited monolayers and analysed using photoluminescence measurements in the temperature range 300–100 K. At reduced temperatures, several excitonic features were observed and the occurrences of these exitonic resonances were found to be stacking angle dependent. Our results indicate that by controlling the stacking angle, it is possible to excite or quench higher order excitations to tune the excitonic flux in optoelectronic devices. We attribute the presence/absence of multiple higher order excitons to the strength of interlayer coupling and doping effect from SiO2/Si substrate. Understanding interlayer excitations will help in engineering excitonic devices and give an insight into the physics of many-body dynamics.


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