tRNA Pseudouridine BACS-Seq | Absolute Base-Resolution Ψ Quantification

Overview

Absolute pseudouridine quantification on tRNA

A modification count is only as useful as its scale. For pseudouridine in tRNA, the question is often not whether a position is modified but what fraction of the tRNA population carries it, because that fraction is what connects the mark to translation and to structure.

Arraystar Single-Nucleotide tRNA Pseudouridine (Ψ) Modification Seq(BACS-seq) is an end-to-end sample-to-data service for tRNA, from RNA sample QC and tRNA treatment through library construction, sequencing and bioinformatics. Sites are localized within mature tRNA transcripts with relative coordinates, gene attribution, anticodon and isotype, and structural-domain context.

What is tRNA BACS-seq?

BACS-seq is an antibody-free, base-resolution method in which controlled bisulfite chemistry protects pseudouridine and reads it as a distinct signature while unmodified bases are converted, enabling absolute base-resolution quantification of Ψ across tRNA.

Service at a Glance

Standard tRNA pseudouridine project — custom designs and add-on analyses available on request

Service Name	Price
Single-Nucleotide tRNA Pseudouridine (Ψ) Modification Seq(BACS-seq)

Benefits

What absolute Ψ quantification adds

Absolute rather than relative levels

Controlled conversion protects Ψ and converts the remaining bases, so the read-out reports the modified fraction itself.

Protected base read directly

The signature sits at the modified position, which keeps resolution at a single nucleotide.

Antibody-free chemistry

No enrichment means no pull-down bias and no cross-reactivity inside compact, structured tRNA.

Mature-tRNA context

Every site carries relative coordinates, host tRNA gene, anticodon, isotype and structural-domain assignment.

Independent of deletion-based routes

Protection chemistry provides a second, chemically distinct line of evidence for the same Ψ position.

Delivered as one project

RNA QC, tRNA treatment, library construction, sequencing and analysis are handled end to end.

Background

From presence calls to absolute pseudouridine levels

Pseudouridine changes how the base attaches to the ribose, which feeds into backbone flexibility and stacking rather than the base-pairing surface alone. In tRNA that is structural information, and its weight depends on how much of the tRNA population at that position is actually modified (1).

Controlled bisulfite chemistry protects pseudouridine and reads it as a distinct signature while unmodified positions are converted and read normally, which is what turns the assay into an absolute measurement. Arraystar applies the chemistry in a tRNA workflow and anchors each site to the mature transcript (1).

tRNA Pseudouridine BACS-Seq Workflow

From total RNA to absolute Ψ levels

The project follows one line from sample to data: RNA QC with small-RNA-retaining purification, tRNA processing and controlled bisulfite treatment, library construction and sequencing, then conversion-aware calling that reports the protected fraction at each position.

tRNA Pseudouridine BACS-Seq Workflow — Figure 2. Single-Nucleotide tRNA Pseudouridine (Ψ) Modification Seq workflow.

Bioinformatics & Deliverables

Bioinformatics for BACS-seq

Reads are aligned to a curated tRNA reference, BACS conversion signatures are called, and per-position stoichiometry is reported with motif, distribution, differential, enrichment and genome-browser results.

Standard Deliverables

Raw sequencing reads (FASTQ) formatted for GEO/SRA deposition.
QC report with sorted BAM files and core mapping statistics.
Single-base Ψ site tables (XLSX) with coordinates, anticodon, isotype and stoichiometry.
Ψ distribution and motif figures across tRNA domains (PDF/PNG).
Differential Ψ tables (XLSX) with fold change and significance.
Genome-browser tracks (bigWig/bedGraph) with a structured tRNA report.

Research Applications

Where absolute Ψ quantification fits

Fraction-level structural questions

Tests how the modified fraction at a position relates to tRNA folding and stability.

Therapeutic and synthetic tRNA work

Quantifies Ψ levels where absolute modification content is the specification.

Decoding and translation

Places absolute Ψ levels in anticodon context relative to decoding outcomes.

Isotype-resolved comparison

Compares protected fraction between tRNA isotypes and isoacceptors.

Disease-oriented screening

Identifies positions whose Ψ fraction shifts between groups.

Sample Requirements

Sample handling and submission for tRNA pseudouridine

Sample Storage

For cells/tissue: use TRIzol or an RNA-stabilizing reagent, quick-freeze in liquid nitrogen, and keep at –80 °C.
For RNA: dissolve in ethanol or RNase-free water, store at –80 °C, and limit freeze–thaw cycles.

Shipping Instructions

Transfer each sample into a 1.5 mL nuclease-free tube.
Close the tube securely with parafilm or a cap lock to preserve integrity.
Send on dry ice with sufficient insulation to sustain the required temperature.

Sample Type	Notes
Whole blood	Use EDTA tubes only; heparin is not compatible with subsequent analytical procedures.
Cultured cells	Cell pellets are preferred to ensure high-quality material for processing.
Tissue	Provide fresh or frozen specimens and avoid necrotic material.
Total RNA	Maintain an OD 260/280 ratio ≥ 1.8 and RIN ≥ 7 with no visible degradation. Submit at least 10 µg total RNA.

Submit at least 10 µg total RNA per sample; the amount includes material consumed by sample QC. Questions: support@arraystar.com

FAQ

Questions we are asked about absolute Ψ quantification

What does absolute quantification change in practice?

Instead of reporting that a position is modified, the assay reports what fraction of the tRNA population carries Ψ there. That fraction is the quantity needed when a threshold, a specification or a comparison between conditions has to be met.

How does protection chemistry identify the site?

Controlled bisulfite treatment leaves pseudouridine shielded while unmodified bases are converted. The protected base therefore stands out as its own signature, which fixes the modification to a single nucleotide instead of to a region of the transcript and keeps the read-out independent of enrichment.

Is antibody enrichment involved?

No. The read-out is chemical, so specificity does not depend on antibody affinity and the workflow avoids the access problems that antibody capture runs into with compact tRNA. Stoichiometry therefore stays comparable between samples and between batches, even for heavily structured targets.

Which features are reported with each site?

Relative coordinates inside the mature tRNA transcript, host tRNA gene attribution, anticodon and isotype, and structural-domain localization. That context is what lets a protected position be interpreted inside the tRNA that carries it rather than as an isolated coordinate, which is what makes the reported fraction biologically interpretable.

How much total RNA is required?

At least 10 µg of total RNA per sample, including the material consumed by sample QC. Samples should show an OD260/280 ratio of 1.8 or higher with no visible degradation, and twice the minimum is recommended to avoid project delays.

How does BACS-seq relate to deletion-based Ψ assays?

Deletion-based assays infer the site from a reverse-transcription deletion, while BACS-seq protects the base and reports it as a retained signature. Using both gives chemically independent evidence for the same position, which is useful when absolute levels are being compared.

Selected Publications

Key references for tRNA pseudouridine

Xu H, Kong L, Cheng J, et al. Absolute quantitative and base-resolution sequencing reveals comprehensive landscape of pseudouridine across the human transcriptome. Nature Methods, 2024. PMID: 39349603

BACS-Seq — Single-Nucleotide tRNA Pseudouridine (Ψ) Modification Seq