Biology subjects

Chimthanawala, A.

Publications and source records attributed to Chimthanawala, A..

3 recordsLinked to original sources

bioRxiv2024

PEPCy: Photostable fluoromodules for live cell, super-resolution microscopy of surface proteins

We report the evolution and application of two genetically encoded tags that bind the cyanine dyes Cy3 or Cy5 with high specificity and selectivity, in addition to enhancing their photostability. These tags, which we call PEPCy, can be used to target membrane proteins such as G-protein coupled receptors. Due to their orthogonality and high binding-affinity for cognate cyanine dyes, the PEPCy tags can be used for wash-free labeling of cell surface receptors to observe their dynamics at a single molecule level. Together with self-labeling tags, these photostability enhancing proteins against cyanine dyes present a novel, complementary and powerful approach to explore protein dynamics with high spatiotemporal resolution.

biophysics↗

bioRxiv2021

SMC protein RecN drives translocation and remodelling of RecA filament for homology search

While the molecular repertoire of the homologous recombination pathway is well-studied, the search mechanism that enables recombination between distant homologous regions is poorly understood. Earlier work suggests that the recombinase RecA, an essential component for homology search, forms an elongated filament, nucleating at the break site. How this RecA structure carries out long distance search remains unclear. Here, we follow the dynamics of RecA after induction of a single double-strand break on the Caulobacter chromosome. We find that the RecA-nucleoprotein filament, once formed, rapidly translocates in a directional manner in the cell, undergoing several pole-to-pole traversals, until homology search is complete. Concomitant with translocation, we observe dynamic remodelling of the filament. Importantly in vivo, the RecA filament alone is incapable of such long distance movement; both translocation and dynamic remodelling are contingent on action of SMC-like protein RecN, via its ATPase cycle. We provide a stochastic description of RecN-regulated changes in filament length during translocation via modulation of RecA assembly-disassembly. In summary, we have uncovered the three key elements of homology search driven by RecN: mobility of a finite segment of RecA, filament remodelling and ability to conduct multiple pole-to-pole traversals, which together point to a novel optimal search strategy.

cell biology↗

bioRxiv2020

Asymmetric chromosome segregation and cell division in DNA damage-induced bacterial filaments

Faithful propagation of life requires coordination of DNA replication and segregation with cell growth and division. In bacteria, this results in cell size homeostasis and periodicity in replication and division. The situation is perturbed under stress such as DNA damage, which induces filamentation as cell cycle progression is blocked to allow for repair. Mechanisms that release this morphological state for re-entry into wild type growth are unclear. Here we show that damage recovery is mediated via asymmetric division of Escherichia coli filaments, producing short daughter cells with wild type size and growth dynamics. Division restoration at this polar site is governed by coordinated action of divisome positioning by the Min system and modulation of division licensing by the terminus region of the chromosome, with MatP playing a central role in this process. Collectively, our study highlights a key role for concurrency between chromosome (and specifically terminus) segregation and cell division in daughter cell size maintenance during filamentous divisions and suggests a central function for asymmetric division in mediating cellular recovery from a stressed state.

microbiology↗