Biology subjects

Troitskaia, A.

Publications and source records attributed to Troitskaia, A..

3 recordsLinked to original sources

bioRxiv2026

Base-pair scale dynamics of a repair helicase on DNA lesions reveal varied damage-sensing mechanisms

Nucleotide excision repair (NER) is a cellular pathway that removes DNA lesions caused by ultraviolet light and various mutagens. A critical component of the NER machinery is XPD helicase, which unwinds the duplex around the damage, allowing its excision and repair. XPD has also been increasingly implicated in sensing and verifying DNA damage. However, the detailed mechanisms by which XPD responds to DNA damage have to-date remained unclear. Here, we use optical tweezers to perform real-time, high-precision measurements of single molecules of XPD as they encounter a variety of well-defined DNA modifications, including a cyclobutane pyrimidine dimer (CPD), a natural substrate for NER. The observed XPD dynamics reveal different behaviors depending on the damage type and the relative orientations of the DNA fork, damage, and helicase. Most notably, XPD displays an almost complete inability to unwind past a CPD on the translocated strand, and instead exhibits a short pause around the lesion--though not a stall--followed by retreat. Combining the base pair-scale XPD kinetics with structural analyses, we identify two regions of XPD sensitive to DNA modifications.

biophysics↗

bioRxiv2021

Individual Molecular Motors use Low Forces to bypass Roadblocks during Collective Cargo Transport

A cargo encounters many obstacles during its transport by molecular motors as it moves throughout the cell. Multiple motors on the cargo exert forces to steer the cargo to its destination. Measuring these forces is essential for understanding intracellular transport. Using kinesin as an example, we measured the force exerted by multiple stationary kinesins in vitro, driving a common microtubule. We find that individual kinesins generally exert less than a piconewton (pN) of force, even while bypassing obstacles, whether these are artificially placed 20-100 nm particles or tau, a Microtubule Associated Protein. We demonstrate that when a kinesin encounters an obstacle, the kinesin either becomes dislodged and then re-engages or switches protofilaments while the other kinesins continue to apply their (sub-)pN forces. By designing a high-throughput assay involving nanometer-resolved multicolor-fluorescence and a force-sensor able to measure picoNewtons of force, our technique is expected to be generally useful for many different types of molecular motors.

biophysics↗

bioRxiv2019

Asymmetric Tug-of-War leads to Cooperative Transport of a Cargo by Multiple Kinesins

How cargoes move within a crowded cell--over long distances and at speeds that are nearly the same as when moving on an unimpeded pathway--has long been mysterious. Through an in vitro gliding assay, which involves measuring nanometer displacement and piconewtons of force, we have evidence that when kinesins, a cytoplasmic molecular motor, operate in small groups, from 2-10, they can communicate among themselves through an asymmetric tug-of-war by inducing tension (up to 4 pN) on the cargo. Surprisingly, the primary role of approximately one-third of kinesins is to develop tension, which instantaneously slows forward motion but helps increase cargo run length. These hindering kinesins fall off rapidly when experiencing a forward tug. Occasionally, they may be ripped off from their anchors by other driving kinesins working in tandem. Furthermore, with roadblocks on the microtubule, multiple kinesins cooperate to overcome impediments. Hence, kinesin may employ an asymmetric tug-of-war and a cooperative motion to navigate through cellular environment.

biophysics↗