Programmable synthetic RNA condensates in mammalian cells

Sequence design

Nanostars had been designed utilizing NUPACK⁵³ on the premise of printed in vitro outcomes¹¹. For every design, ten NUPACK trials had been run, and the one which generated the bottom defect rating was chosen. Broccoli, Pepper, Mango and MS2 aptamer sequences had been taken from literature^18,20,34,54. The wild-type KL (5′-GCGCGC) was tailored from the HIV-1 palindromic KL sequence³². Orthogonal KLs 5′-UCGCGA, 5′-GUCGAC and 5′-GGUACC had been taken from the examine by Fabrini et al.¹². KLs 5′-GUAUAC and 5′-UAUAUA had been designed by merely changing GC pairs with AU pairs. Non-palindromic KLs had been tailored from the 3sβ set designed by Stewart et al.¹¹. Detailed design ideas of nanostar stems and KLs could be present in Supplementary Section 1.1. All sequences are listed in Supplementary Table 1.

RNA synthesis for in vitro characterization

All RNA strands for in vitro experiments had been transcribed from customized DNA templates synthesized by Integrated DNA Technologies as LabReady resuspensions with customary desalt purification. We annealed non-coding DNA templates with a 21-nt complement together with the T7 promoter area and a 4-nt sealing area (5′-GCGC). These templates had been annealed in 1× TE/50 mM NaCl from 90 °C to room temperature at −1 °C min⁻¹ at 5 μM for storage and used at 0.01 μM throughout in vitro transcription. RNA strands had been transcribed in vitro at 37 °C utilizing 7.5% (v/v) T7 polymerase from the AmpliScribe T7-Flash transcription equipment (ASF3507, Biosearch Technologies), and transcription buffer ready in-house: 40 mM of Tris-HCl, 10 mM of NaCl, 30 mM MgCl₂, 2 mM spermidine, 7.5 mM of every NTP and 10 mM DTT.

Plasmid growth

Inserts had been immediately bought from Integrated DNA Technologies as two single-stranded, 5′-phosphorylated oligonucleotides containing the sequence of curiosity, flanked by NotI and SacII restriction websites. The two strands had been annealed in 50 mM NaCl and 1× TE buffer utilizing a warmth remedy protocol together with a 5-min soften at 90 °C, adopted by a gradual temperature ramp at −1 °C min⁻¹, and held at 20 °C. The ensuing merchandise had been double-stranded DNA fragments with sticky ends prepared for ligation. After annealing, strands had been purified with a DNA cleanup equipment (NEB, T1030). The DNA encoding the nanostar sequences was inserted within the pAV-U6+27-Tornado-Broccoli (Addgene, 261587) plasmid. Plasmids had been ready by (1) digestion with NotI-HF (NEB, R3189S) (2 μl for 20-μl reactions) at 37 °C for 1 h, (2) purification with the DNA cleanup equipment, (3) digestion with SacII (NEB, R0157S) (2 μl for 20-μl reactions) at 37 °C for 1 h and (4) purification with a 0.8% 1× TAE agarose gel to pick the product with the proper dimension. Digested backbones had been lastly purified utilizing a gel extraction equipment (Qiagen, 28704). Digested spine and inserts had been ligated at a 1:10 molecular ratio by in a single day incubation with T4 DNA ligase (NEB, M0202S) at 4 °C. Ligated plasmids had been remodeled into 50 μl DF5Hα competent cells (Thermo Fisher, EC0112 and 18258012) following the producer’s protocol. We then extracted plasmid DNA utilizing a Miniprep equipment (Qiagen, 27106) following the producer’s protocol. Extracted plasmids had been lastly sequenced by Eurofins Genomics (entire plasmid sequencing service). The plasmid expressing MCP-mCherry was bought from Addgene (207668)⁵⁵.

Cell tradition and upkeep

HEK293T (ATCC, CRL-3216), HeLa (ATCC, CCL-2) and U-2 OS (ATCC, HTB-96) cells had been grown in Dulbecco modified Eagle’s medium (DMEM), excessive glucose, pyruvate (Thermo Fisher, 11995065) containing 10% fetal bovine serum and 100 U ml⁻¹ penicillin–streptomycin (Thermo Fisher) and maintained at 37 °C with 5% CO₂ in a humidified incubator. Cells used for imaging had been cultured in µ-Slide 8-well excessive slides (Ibidi GmbH).

Transfection

Seeding density was tailored throughout cell sorts to realize ~70% confluence at transfection. Lipofectamine 2000 (Thermo Fisher, 11668019) was used for transfecting HEK293T cells. FuGene HD (Promega, E2311) was used for transfecting HeLa and U-2 OS cells because it demonstrated much less cytotoxicity as a consequence of transfection. For experiments involving the expression of a number of nanostars, the overall quantity of plasmid DNA utilized in every experiment was stored fixed, with an equal proportion of every nanostar variant.

Total RNA extraction

Cells had been transfected in 24-well plates, as described in Supplementary Section 1.5. We modified the medium 24 h after transfection, and picked up cells 48 h after transfection. For assortment, we aspirated media, washed with PBS and trypsinized the cells. After trypsinization, cells had been resuspended in PBS, lysed and RNA was purified utilizing the Monarch Total RNA Miniprep Kit (NEB, T2010S). RNA focus was estimated utilizing a Nanodrop 2000c by measuring absorption at 260 nm.

Live-cell staining

The tradition medium from in a single day incubation was aspirated and changed with contemporary medium supplemented with two drops of NucBlue Live reagent (Hoechst 33342 nuclear dye, Thermo Fisher, R37605) per millilitre of media, together with the suitable staining dyes in keeping with experimental circumstances. For circumstances involving the Broccoli aptamer, we used 40 µM of DFHBI (Lucerna; 400-5 mg). For experiments involving the Pepper aptamer, we equipped 10 nM of HBC620 (MedChemExpress, HY-133520). Live cells had been then incubated for at the least 15 min at 37 °C earlier than imaging. Cells had been imaged within the presence of dyes.

Fixed cell staining and immunostaining

Mouse anti-coilin (Cajal physique colocalization) was bought from Abcam (ab11822; 1:1,900, 1 μg ml⁻¹). Mouse anti-SC35 (nuclear speckle colocalization) was bought from Abcam (ab11826; 1:200, 5 μg ml⁻¹). Mouse anti-fibrillarin (nucleolus colocalization) was bought from Antibodies.com (A85370; 1:200). Mouse anti-G3BP1 (stress granules colocalization) was bought from Thermo Fisher (66486-1-IG; 1:200, 5 μg ml⁻¹). Mouse anti-DCP1A (P-body colocalization) was bought from Novus Biological (H00055802-M06; 1:200).

Before fixation, cell tradition media had been eliminated and cells had been rinsed with PBS (Thermo Fisher, 10010023). Cells had been then fastened in a PBS buffer (Thermo Fisher, 14190144) containing 4% paraformaldehyde (Thermo Fisher, 043368.9M) for 10 min at room temperature, and washed with the PBS buffer thrice, every for five min. Next, we permeabilized cells with 0.5% Triton X-100 (Sigma-Aldrich, 9002-93-1) in PBS buffer for 10 min and washed thrice. For imaging condensates involving the Mango aptamer, we added PBS supplemented with NucBlue reagent (Thermo Fisher, R37605) and 200 nM of TO1-B (ABM, G955). Cells had been incubated within the buffer for 15 min earlier than imaging. For experiments involving immunostaining, cells had been additional blocked utilizing 3% bovine serum albumin (BSA) (w/v; Sigma-Aldrich, 9048-46-8) in PBS buffer for 1 h, and washed thrice. Then, cells had been stained with corresponding main antibodies diluted to the above-mentioned concentrations with 3% BSA in PBS buffer and incubated at 4 °C in a single day. The subsequent day, main antibodies had been eliminated and cells had been washed thrice earlier than the addition of secondary antibodies (Thermo Fisher, A-21236; 1:1,000 in 3% BSA in PBS buffer). We incubated cells in secondary antibodies for 1 h earlier than eradicating the buffer and washing them thrice with PBS. For the ultimate wash, PBS was supplemented with 40 μM DFHBI and NucBlue reagent. Cells had been incubated within the buffer for 15 min earlier than imaging.

Microscopy

FRAP and fusion experiments had been carried out with epifluorescence imaging utilizing a Nikon Eclipse TI-E inverted microscope and a 60× oil immersion goal. z-Stack confocal photographs had been acquired utilizing a Nikon Ti microscope outfitted with an NL5+ digicam. Images in Fig. 4d,okay had been captured utilizing a Yokogawa CSU X1 spinning disk confocal on an inverted Zeiss stand. Hoechst (NucBlue staining) alerts had been detected within the UV channel (excitation 405 nm). Broccoli aptamer fluorescence was measured utilizing the GFP channel (excitation 488 nm). Mango aptamer fluorescence was measured utilizing the YFP channel (excitation 514 nm). Pepper aptamer, CY3 and mCherry fluorescence was detected utilizing the RFP channel (excitation 561 nm). Finally, Alexa Fluor 647-labelled secondary antibody fluorescence was detected utilizing the 647 nm channel (excitation 647 nm).

Image processing

To present a extra complete view of condensate alerts throughout all planes, confocal micrographs within the manuscript figures are max-pixel-intensity z-projections, until in any other case specified within the determine caption. Detailed knowledge processing strategies and schematics could be present in Supplementary Information, together with condensate quantity and quantity quantification, nucleus quantity quantification, partition coefficient calculation for linked condensates (J_R and J_G), partition coefficient calculation for peptides and small-molecule dye, and the PCC and Manders’ overlap coefficient (M1 and M2) calculation.

FRAP

FRAP experiments had been carried out utilizing a Nikon Eclipse TI-E inverted microscope with a temperature management unit. In vitro samples had been loaded right into a house-made chamber and sealed with epoxy (Gorilla, 5-min set) for imaging. For in vivo experiments, cells had been stained and imaged within the Ibidi chamber described above. Condensates had been bleached with a 488-nm laser for 200 ms. For in vitro samples, imaging was captured as soon as earlier than bleaching and each 5 s for 10 min after bleaching. For in vivo samples, imaging was captured as soon as earlier than bleaching and each 200 ms for two min after bleaching or each 1.5 s for five min after bleaching. Images had been analysed by extracting time-dependent common intensities throughout the bleached space and unbleached space. Data processing and becoming particulars are described in Supplementary Information.

Time-dependent coalescence evaluation

For in vitro experiments, RNA strands had been transcribed, labelled with 1% CY3-UTP, diluted ten instances with transcription buffer and sealed in a chamber with epoxy, following the identical protocol as FRAP experiments. Samples had been imaged each 5 min for the primary 4 h, then each 20 min till 10 h. We monitored condensate fusion occasions utilizing a Nikon Eclipse TI-E inverted microscope with a temperature management unit. The temperature was maintained at 37 °C for all experiments.

For in vivo fusion experiments, we imaged cells (in media supplemented with 40 μM DFHBI and a pair of drops ml⁻¹ NucBlue) each 5 min for 60 min beneath the confocal microscope. The temperature was maintained at 37 °C. Fusion occasions had been recognized manually. Data processing was carried out utilizing a script in Python3, as described in our earlier work¹¹.

Flow cytometry

Flow cytometry experiments had been carried out utilizing a BD FACSAria circulate cytometer. Cells had been transfected in 24-well plates, as described in Supplementary Section 1.5. We modified the media 24 h after transfection, and picked up cells 48 h after transfection. For assortment, we aspirated media, washed with PBS and trypsinized the cells. After trypsinization, cells had been resuspended in PBS supplemented with 10% fetal bovine serum and dyes and filtered by means of a 40-μm cell strainer (Fisher Scientific, cat. no. 22363547) for circulate cytometry. Hoechst was detected utilizing a laser with Ex. 405 nm and a 450/50-nm filter; DFHBI was detected utilizing a laser with Ex. 488 nm and a 530/30-nm filter.

RT–qPCR

Reverse transcription was carried out with equal quantities of RNA utilizing the Protoscript II First Strand cDNA Synthesis Kit and random hexamers (New England Biolabs). Reverse-transcription quantitative PCR (RT–qPCR) was then carried out utilizing tenfold diluted cDNA and the Luna Universal qPCR Master Mix (New England Biolabs) within the CFX Real-Time PCR system (Bio-Rad), courtesy of the UCLA Virology Core. The qPCR circumstances used had been as beforehand described^56,57. Target transcript ranges had been decided by normalizing the cycle threshold worth of the goal transcript to that of the housekeeping gene RPS11 transcript. Fold change was calculated utilizing this normalized worth relative to Lipofectamine management expression ranges. For RT–qPCR primers, see Supplementary Table 4.

Polyacrylamide gel electrophoresis

Gel pre-mix was ready by including 42 g of urea to nanopure water, the combination was then heated till the urea fully dissolved. This combination was allowed to chill to room temperature, after which a 40% (v/v) 19:1 acrylamide:bis-acrylamide resolution was added within the acceptable quantity for the specified proportion (last quantity of 100 ml). To begin polymerization, 8 ml of pre-mix was added in acceptable ratios with TBE and nanopure water, ammonium persulfate and tetramethylethylenediamine. Gels had been solid in 8 cm × 8 cm, 1-mm-thick disposable mini gel cassettes (Thermo Scientific, NC2010) and allowed to polymerize for 30 min earlier than electrophoresis. After curing, the gel was pre-run in a 1× TBE buffer for 30 min. Wells had been washed fastidiously to take away extreme urea. Samples and a low-range ssRNA ladder (NEB, N0364S) had been ready by mixing particular person strands with denaturing RNA loading dye (NEB, B0363S), then heated at 70 °C for 10 min and instantly positioned on ice. Owing to the low expression of exogenous RNA in mammalian cells, 5 μg of complete RNA extraction was loaded into every nicely. Gels had been run at room temperature at 100 V in 1× TBE until in any other case famous. After electrophoresis, the gels had been washed thrice, every for five min, with nanopure water, then stained with DFHBI-1T staining buffer (10 μM DFHBI-1T, 40 mM HEPES, 100 mM KCl and 1 mM MgCl₂) for 15 min. After staining, gels had been imaged utilizing the Bio-Rad Gel Imaging Systems. Then, gels had been washed thrice, every for five min, to take away the DFHBI-1T and stained in 1× SYBR Gold Nucleic Acid Gel Stain for 15 min and imaged once more.

Statistics and reproducibility

At least three impartial organic replicates had been examined for every situation. For microscopy imaging, at the least three completely different fields of view had been captured for every replicate. No knowledge had been excluded from the analyses.