Mutations in a number of stress granule-associated proteins have been linked to various neurodegenerative diseases. Several of these mutations are found in aggregation-prone prion-like domains (PrLDs) within these proteins. In this work, we examine the sequence features governing PrLD localization to stress granules upon stress. We demonstrate that many yeast PrLDs are sufficient for stress-induced assembly into microscopically visible foci that colocalize with stress granule markers. Additionally, compositional biases exist among PrLDs that assemble upon stress, and these biases are consistent across different stressors. Using these biases, we have developed a composition-based prediction method that accurately predicts PrLD assembly into foci upon heat shock. We show that compositional changes alter PrLD assembly behavior in a predictable manner, while scrambling primary sequence has little effect on PrLD assembly and recruitment to stress granules. Furthermore, we were able to design synthetic PrLDs that were efficiently recruited to stress granules, and found that aromatic amino acids, which have previously been linked to PrLD phase separation, were dispensable for this recruitment. These results highlight the flexible sequence requirements for stress granule recruitment and suggest that PrLD localization to stress granules is driven primarily by amino acid composition, rather than primary sequence.

Many aspects of bacterial physiology and behavior, including motility, surface attachment, and the cell cycle, are controlled by cyclic di-GMP (c-di-GMP)-dependent signaling pathways on the scale of seconds to minutes. Interrogation of such processes in real time requires tools for introducing rapid and reversible changes in intracellular c-di-GMP levels. Inducing the expression of genes encoding c-di-GMP-synthetic (diguanylate cyclases) and -degrading (c-di-GMP phosphodiesterase) enzymes by chemicals may not provide adequate temporal control. In contrast, light-controlled diguanylate cyclases and phosphodiesterases can be quickly activated and inactivated. A red/near-infrared-light-regulated diguanylate cyclase, BphS, was engineered previously, yet a complementary light-activated c-di-GMP phosphodiesterase has been lacking. In search of such a phosphodiesterase, we investigated two homologous proteins from Allochromatium vinosum and Magnetococcus marinus, designated BldP, which contain C-terminal EAL-BLUF modules, where EAL is a c-di-GMP phosphodiesterase domain and BLUF is a blue light sensory domain. Characterization of the BldP proteins in Escherichia coli and in vitro showed that they possess light-activated c-di-GMP phosphodiesterase activities. Interestingly, light activation in both enzymes was dependent on oxygen levels. The truncated EAL-BLUF fragment from A. vinosum BldP lacked phosphodiesterase activity, whereas a similar fragment from M. marinus BldP, designated EB1, possessed such activity that was highly (Ͼ30-fold) upregulated by light. Following light withdrawal, EB1 reverted to the inactive ground state with a half-life of ϳ6 min. Therefore, the bluelight-activated phosphodiesterase EB1 can be used in combination with the red/nearinfrared-light-regulated diguanylate cyclase BphS for the bidirectional regulation of c-di-GMP-dependent processes in E. coli as well as other bacterial and nonbacterial cells.IMPORTANCE Regulation of motility, attachment to surfaces, the cell cycle, and other bacterial processes controlled by the c-di-GMP signaling pathways occur at a fast (seconds-to-minutes) pace. Interrogation of these processes at high temporal and spatial resolution using chemicals is difficult or impossible, while optogenetic approaches may prove useful. We identified and characterized a robust, blue-lightactivated c-di-GMP phosphodiesterase (hydrolase) that complements a previously engineered red/near-infrared-light-regulated diguanylate cyclase (c-di-GMP synthase). These two enzymes form a dichromatic module for manipulating intracellular c-di-GMP levels in bacterial and nonbacterial cells.KEYWORDS biofilms, c-di-GMP, diguanylate cyclase, gene expression, motility, optogenetics, phosphodiesterase, photoreceptors, photosensory reception, signal transduction S ignaling via second messengers occurs at various time scales, from seconds to hours. To control relatively slow processes, intracellular concentrations of a second messenger can be modulated by the constitutive or inducible (over)e...

Multicellular organisms achieve greater complexity through cell divisions that generate different cell types. We engineered a simple genetic circuit that induces asymmetric cell division and subsequent cell differentiation in Escherichia coli . The circuit involves a scaffolding protein, PopZ, that is stably maintained at a single cell pole over multiple asymmetric cell divisions. PopZ was functionalized to degrade the signaling molecule, c-di-GMP. By regulating synthesis of functionalized PopZ via small molecules or light, we can chemically or optogenetically control the relative abundance of two distinct cell types, characterized by either low or high c-di-GMP levels. Differences in c-di-GMP levels can be transformed into genetically programmable differences in protein complex assembly or gene expression, which in turn produce differential behavior or biosynthetic activities. This study shows emergence of complex biological phenomena from a simple genetic circuit and adds programmable bacterial cell differentiation to the genetic toolbox of synthetic biology and biotechnology.

Light in the near-infrared optical window (NIRW) penetrates deep through mammalian tissues, including the skull and brain tissue. Here we engineered an adenylate cyclase (AC) activated by NIRW light (NIRW-AC) and suitable for mammalian applications. To accomplish this goal, we constructed fusions of several bacterio­phytochrome photosensory and bacterial AC modules using guidelines for designing chimeric homodimeric bacterio­phytochromes. One engineered NIRW-AC, designated IlaM5, has significantly higher activity at 37 °C, is better expressed in mammalian cells, and can mediate cAMP-dependent photoactivation of gene expression in mammalian cells, in favorable contrast to the NIRW-ACs engineered earlier. The ilaM5 gene expressed from an AAV vector was delivered into the ventral basal thalamus region of the mouse brain, resulting in the light-controlled suppression of the cAMP-dependent wave pattern of the sleeping brain known as spindle oscillations. Reversible spindle oscillation suppression was observed in sleeping mice exposed to light from an external light source. This study confirms the robustness of principles of homodimeric bacterio­phytochrome engineering, describes a NIRW-AC suitable for mammalian optogenetic applications, and demonstrates the feasibility of controlling brain activity via NIRW-ACs using transcranial irradiation.

Stress granules are ribonucleoprotein assemblies that form in response to cellular stress. Many of the RNA-binding proteins found in stress granule proteomes contain prion-like domains (PrLDs), which are low-complexity sequences that compositionally resemble yeast prion domains. Mutations in some of these PrLDs have been implicated in neurodegenerative diseases, including amyotrophic lateral sclerosis and frontotemporal dementia, and are associated with persistent stress granule accumulation. While both stress granules and prions are macromolecular assemblies, they differ in both their physical properties and complexity. Prion aggregates are highly stable homopolymeric solids, while stress granules are complex dynamic biomolecular condensates driven by multivalent homotypic and heterotypic interactions. Here, we use stress granules and yeast prions as a paradigm to examine how distinct sequence and compositional features of PrLDs contribute to different types of PrLD-containing assemblies.

The modern concepts of programmed cell death (PCD) in plants are reviewed as compared to PCD (apoptosis) in animals. Special attention is focused on considering the potential mechanisms of implementation of this fundamental biological process and its participants. In particular, the proteolytic enzymes involved in PCD in animals (caspases) and plants (phytaspases) are compared. Emphasis is put on elucidation of both common features and substantial differences of PCD implementation in plants and animals.

Signaling pathways involving second messenger c-di-GMP regulate various aspects of bacterial physiology and behavior. We describe the use of a red light-activated diguanylate cyclase (c-di-GMP synthase) and a blue light-activated c-di-GMP phosphodiesterase (hydrolase) for manipulating intracellular c-di-GMP levels in bacterial cells. We illustrate the application of these enzymes in regulating several c-di-GMP-dependent phenotypes, i.e., motility and biofilm phenotypes in E. coli and chemotactic behavior in the alphaproteobacterium Azospirillum brasilense. We expect these light-activated enzymes to be also useful in regulating c-di-GMP-dependent processes occurring at the fast timescale, for spatial control of bacterial populations, as well as for analyzing c-di-GMP-dependent phenomena at the single-cell level.

Hepatitis C virus (HCV) causes both acute and chronic disease of the liver that can lead to liver cirrhosis, cancer and liver failure. HCV is characterized by high genetic diversity and substantial variations in prevalence of specific HCV genotypes in different countries of the world. Many effective regimens of direct-acting antivirals (DAAs), including pan-genotypic, can successfully treat HCV infection. However, genotype-specific treatments for HCV are being actively employed in the national plans for elimination of HCV infection around the world. Evaluation of HCV genotype prevalence in a country is mandatory for successful implementation of the national plans for elimination of HCV infection and allocation of financial resources to DAAs most effecting for specific HCV genotypes prevalent in a country. Here, we analyzed HCV genotypes, subgenotypes and recombinants in 10,107 serum samples from patients with chronic HCV infection from all Federal districts of Russia collected in 2015-2017. This is the first, largest evaluation of HCV genotypes performed on samples from all territories of Russia, from its Central Federal district to the Far East. Moreover, we have updated retrospective epidemiological analysis of chronic and acute HCV infection in Russia in 2001-2021. We demonstrate that the incidence of acute HCV infection in Russia reduced from 16.7 cases per 100,000 population in 2001 to 0.6 cases per 100,000 population in 2021. The number of cases of chronic HCV infection decreased from 29.5 to 16.4 per 100,000 population during this period. HCV genotype analysis indicated that HCV genotype 1 dominates in Russia (53.6%). Genotypes 3 and 2 were detected in 35.4% and 7.8% of patients respectively. These proportions are virtually identical in all regions of Russia except for Far East, where HCV genotype 2 amounts only to 1%. HCV genotypes 1 and 2 are more widespread in women, while HCV genotype 3 in men. The highest frequency of identification of genotype 3 was found in the age group of 31-40 years old (44.9%, respectively), and genotype 1 was more prevalent in a group of over 70 years old (72.2%). The proportion of HCV genotype 2 is predominant among HCV-infected persons older than 40 years. Discriminating HCV genotype 2 and recombinant RF1_2k/1b, which are frequently misclassified, is important for successful antiviral treatment of such patients. For the first time, we demonstrate the countrywide prevalence of HCV RF1_2k/1b in different regions of Russia. HCV RF1_2k/1b amounts to 3.2% in the structure of HCV genotypes, reaching 30% among samples classified as genotype 2 by some commercial genotyping tests. The highest proportion of HCV RF1_2k/1b was detected in the north-west (60%), southern (41.6%) and central (31.6%) federal district. Its frequency in Far Eastern and North Caucasus Districts was ~ 14.3%. HCV RF1_2k/1b was not detected in the Volga, Ural and Siberian districts. To conclude, this is the first and most complete evaluation of HCV epidemiology and genotype/subgenotype distribution in Russia.