Transcription-coupled DNA supercoiling has been shown to be an important regulator of transcription that is broadly present in the cell. Here we review experimental work which shows that RNA polymerase is a powerful torsional motor that can alter DNA topology and structure, and DNA supercoiling in turn directly affects transcription elongation. © 2014 Landes Bioscience.

We show ability to simultaneously trap micron-size particles in an optical field and freeze their position by rapidly changing the direction of Poynting vector in an optofluidic waveguide using an electrically controlled Mach-Zehnder switch. © 2014 OSA.

Optical trapping is a powerful manipulation and measurement technique widely used in the biological and materials sciences. Miniaturizing optical trap instruments onto optofluidic platforms holds promise for high-throughput lab-on-a-chip applications. However, a persistent challenge with existing optofluidic devices has been achieving controlled and precise manipulation of trapped particles. Here, we report a new class of on-chip optical trapping devices.

Remodeling of the local chromatin structure is essential for the regulation of gene expression. While a number of biochemical and bioimaging experiments suggest decondensed chromatin structures are associated with transcription, a direct visualization of DNA and transcriptionally active RNA polymerase II (RNA pol II) at super-resolution is still lacking. Here we investigate the structure of chromatin isolated from HeLa cells using binding activatable localization microscopy (BALM). The sample preparation method preserved the structural integrity of chromatin.

Mechanical manipulations of single biological molecules have revealed highly dynamic and mechanical processes at the molecular level. Recent developments have permitted examination of the impact of torque on these processes and visualization of detailed molecular motions, enabling studies of increasingly complex systems. Here we highlight some recent important discoveries. © 2014 Elsevier Inc.

The genome of bacteria is organized and compacted by the action of nucleoid-associated proteins. These proteins are often present in tens of thousands of copies and bind with low specificity along the genome. DNA-bound proteins thus potentially act as roadblocks to the progression of machinery that moves along the DNA. In this study, we have investigated the effect of histone-like protein from strain U93 (HU), one of the key proteins involved in shaping the bacterial nucleoid, on DNA helix stability by mechanically unzipping single dsDNA molecules.

The nucleosome, the fundamental packing unit of chromatin, has a distinct chirality: 147 bp of DNA are wrapped around the core histones in a left-handed, negative superhelix. It has been suggested that this chirality has functional significance, particularly in the context of the cellular processes that generate DNA supercoiling, such as transcription and replication. However, the impact of torsion on nucleosome structure and stability is largely unknown.

The introduction of chemical inhibitors into living cells at specific times in development is a useful method for investigating the roles of specific proteins or cytoskeletal components in developmental processes. Some embryos, such as those of Caenorhabditis elegans, however, possess a tough eggshell that makes introducing drugs and other molecules into embryonic cells challenging. We have developed a procedure using carbon-reinforced nanopipettes (CRNPs) to deliver molecules into C. elegans embryos with high temporal control.

Single-molecule experiments have shed new light on the mechanisms responsible for the movement of RNA polymerase along DNA during transcription. © Forties et al.