tRNA m7G Quant-Seq | Base-Resolution m⁷G Mapping and Quantification

Overview

Quantifying the m⁷G fraction on tRNA

N7-methylguanosine carries a positive charge on the modified guanine, which changes how the base behaves and how the surrounding structure folds. In tRNA it sits in structured regions of a compact, heavily modified molecule, so a useful assay resolves individual positions rather than reporting one bulk level.

Arraystar Single-Nucleotide tRNA m⁷G Modification Seq(m7G-Quant-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 m7G-Quant-Seq?

m⁷G-Quant-Seq is a base-resolution method in which targeted chemical conversion records N7-methylguanosine as a discrete reverse-transcription signature, so m⁷G is detected and quantified across tRNA at single-nucleotide resolution.

Service at a Glance

Standard m⁷G project — custom designs and add-on analyses available on request

Service Name	Price
Single-Nucleotide tRNA m⁷G Modification Seq(m7G-Quant-Seq)

Benefits

Why m⁷G needs its own assay

Position-resolved, not bulk

Conversion signatures are called per position on a curated tRNA reference, so the result is a set of individual m⁷G sites rather than one averaged level.

Quantified rather than merely detected

Each position yields a modification fraction, allowing m⁷G levels to be compared between samples.

Antibody-free chemistry

The read-out is chemistry-based, which suits the compact, structured environment of tRNA.

Annotated within mature tRNA

Sites carry relative coordinates, host tRNA gene, anticodon, isotype and structural-domain assignment.

Independent of cleavage methods

The quantitative conversion route provides a separate line of evidence from cleavage-based m⁷G sequencing.

Delivered end to end

RNA QC, tRNA treatment, library construction, sequencing and analysis are handled as one project.

Background

Why m⁷G quantification is harder than it looks

N7-methylguanosine modifies the base in a way that changes its charge and its stacking behaviour, and in tRNA it contributes to structure and function. Its positions are few and spread over different domains, so a bulk measurement averages those differences away - the useful readout is per position (1).

Targeted chemical conversion acts on the modified base and records it as a distinct reverse-transcription signature, so each m⁷G site is read at base resolution and quantified from the converted fraction. Arraystar applies the chemistry in a tRNA workflow and reports every site with its tRNA context (1).

tRNA m7G-Quant-Seq Workflow

From total RNA to m⁷G stoichiometry

Total RNA passes sample QC and small-RNA-retaining purification, then tRNA treatment and targeted chemical conversion, library construction and sequencing, after which conversion-aware alignment and per-site quantification produce the m⁷G map.

tRNA m7G-Quant-Seq Workflow — Figure 2. Single-Nucleotide tRNA m⁷G Modification Seq workflow.

Bioinformatics & Deliverables

Bioinformatics for m7G-Quant-Seq

Reads are mapped to a curated tRNA reference, conversion signatures are called as m⁷G positions, 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 m⁷G site tables (XLSX) with coordinates, anticodon, isotype and stoichiometry.
m⁷G distribution and motif figures across tRNA domains (PDF/PNG).
Differential m⁷G tables (XLSX) with fold change and significance.
Genome-browser tracks (bigWig/bedGraph) with a structured tRNA report.

Research Applications

Where m⁷G quantification fits

tRNA structural biology

Links m⁷G at a defined position to tRNA folding and stability.

Writer and eraser studies

Tests how methyltransferase or demethylase perturbations change m⁷G levels.

Cross-checks with cleavage methods

Provides an independent, conversion-based line of evidence alongside cleavage-based m⁷G mapping.

Isotype-resolved analysis

Compares m⁷G occupancy between tRNA isotypes and isoacceptors.

Disease-oriented screening

Identifies differentially methylated tRNA positions between groups.

Sample Requirements

Sample handling and submission for m⁷G

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 m⁷G quantification

Why report m⁷G per position rather than as a bulk level?

Because m⁷G positions are few and sit in different domains, a bulk measurement averages them together. The conversion signature is called per position on a curated tRNA reference, so each site is quantified in its own right and can be compared between samples.

Is m⁷G reported as a fraction or as a call?

As a fraction. The converted proportion at each position gives the modification level, so the same site can be compared quantitatively between samples rather than only being reported as present or absent. That is what makes m⁷G usable in a comparative study.

Which tRNA features are annotated?

Sites are reported with relative coordinates inside the mature tRNA transcript, host tRNA gene attribution, anticodon and isotype, and structural-domain localisation, so each m⁷G call can be read in the context of the tRNA that carries it rather than as a coordinate alone.

Where does m⁷G sit in tRNA and what does it do?

Within tRNA, m⁷G at position 46 in the variable loop is the best-characterised site, where it stabilises the folded core of the molecule. Because every call carries its relative coordinate and structural domain, a change in the quantified fraction can be interpreted against that structural role.

How does this relate to cleavage-based m⁷G sequencing?

The two use different chemistry to reach the same modification. Running the quantitative conversion route alongside a cleavage-based method provides independent evidence for a site and cross-checks the reported levels, which is useful when m⁷G is compared across conditions.

Can differential m⁷G be tested between conditions?

Yes. Per-position stoichiometry is reported for each sample, and differential analysis with fold change and significance is part of the standard pipeline, so shifts in m⁷G can be called directly at the level of individual tRNA positions across a time course.

m7G-Quant-Seq — Single-Nucleotide tRNA m⁷G Modification Seq