UBS-seq (ultrafast bisulfite sequencing) is a bisulfite conversion method developed by researchers at the University of Chicago that converts unmethylated cytosines to uracil in as little as 10 minutes or less, allowing the total methyl conversion protocol to be completed in under an hour — compared with conventional bisulfite kit protocols that take from 160 minutes to as long as overnight. UBS-seq uses highly concentrated ammonium bisulfite/sulfite reagents at 98 °C to accelerate the chemistry roughly 13-fold, resulting in highly efficient C-to-T conversion, lower background noise, and more accurate 5-methylcytosine (5mC) and RNA m5C detection — even from single cells, cell-free DNA (cfDNA), or low-input RNA.
What Problem Does UBS-seq Solve?
Bisulfite sequencing (BS-seq) has been the gold-standard method for mapping 5-methylcytosine since 1992, but conventional protocols have well-known limitations (Zymo’s EZ DNA Methylation-Gold Kit was used for benchmarking):
- Long reaction times. Conventional bisulfite conversion methods require relatively long reaction times. Depending on the protocol, the conversion step can take anywhere from 68 minutes to overnight, limiting workflow efficiency and throughput.
- DNA damage. Extended exposure to bisulfite severely degrades the treated DNA through a process called depyrimidination.
- Incomplete C-to-U conversion, especially in high-GC or highly structured regions like mitochondrial DNA, which creates false positives.
- Overestimation of methylation levels, because unmethylated (and therefore more heavily converted and degraded) DNA fragments are lost disproportionately during long treatments, and also because of incomplete C-to-U conversion.
- Incomplete 4-methylcytosine (4mC) deamination (~50% under conventional conditions), which can be misread as 5mC.
The study — led by Professor Chuan He (University of Chicago / Howard Hughes Medical Institute) with researchers Qing Dai, Chang Ye, Iryna Irkliyenko, and Yiding Wang — reported fixing all five problems at once. The team published their findings in Nature Biotechnology in 2024 as “Ultrafast bisulfite sequencing detection of 5-methylcytosine in DNA and RNA.”
How Does UBS-seq Work?
Bisulfite conversion happens through two competing chemical pathways: one that produces the desired C-to-U conversion, and one that leads to unwanted DNA degradation. Both pathways depend on bisulfite reagent concentration. The researchers reasoned that if they used a much higher effective concentration of bisulfite and a higher reaction temperature, they could drive the conversion reaction to completion in minutes rather than hours — leaving far less time for degradation to occur.
Key Findings from the Paper
Less DNA damage
Gel electrophoresis confirmed that UBS-seq-treated genomic DNA showed slightly less fragmentation than DNA treated under the conventional bisulfite condition.
Quantitative 4mC deamination
Under UBS-seq conditions, both 4mC and unmodified C were read as T with near-quantitative efficiency, while conventional bisulfite treatment converted only about half of 4mC sites — a major source of false positives in genomes containing this modification.
Dramatically lower background
On unmethylated lambda (λ) DNA, 10-minute UBS-seq treatment produced an average unconverted rate of just ~0.06%, versus more than 13-fold higher background for the 3-hour treatment using the conventional bisulfite conversion method.
Works from vanishingly small inputs
UBS-seq successfully generated methylation libraries from 1 to 100 mouse embryonic stem cells, and from as little as 7.5 ng of human plasma cell-free DNA (cfDNA), with ~20-fold lower background than conventional BS-seq at the single-cell level. This makes it especially promising for liquid biopsy and cancer diagnostic applications, where input DNA is inherently limited.
A proof-of-concept cancer application
Applying UBS-seq to cfDNA from patients with early-onset colorectal cancer (EOCRC) versus healthy controls, the researchers identified 135 differentially methylated regions as candidate biomarkers — even in regions where methylation differences were relatively subtle.
Accurate RNA m5C mapping, including in highly structured RNA
A modified recipe extended the same ultrafast chemistry to RNA. Applied to human 28S ribosomal RNA, UBS-seq detected known m5C sites with >95% efficiency and a 0% false-positive rate at a 5% detection threshold — outperforming a commercial RNA bisulfite kit (which had an ~18% false-positive rate) and three previously published protocols. UBS-seq also successfully mapped m5C sites within human tRNA, a molecule so tightly folded that older methods routinely struggled with incomplete conversion in its structured regions.
New biological insight into mRNA m5C
Applying UBS-seq to polyA-selected mRNA from HeLa and HEK293T cells, the team identified thousands of high-confidence m5C sites: 2,723 in HeLa and 2,404 in HEK293T mRNA. Knockdown experiments showed that NSUN2 is responsible for depositing roughly 90% of m5C sites in HeLa mRNA, with a smaller subset installed by NSUN6 on a distinct CUCCA sequence motif. The study also found that NSUN2-deposited m5C sites are enriched near the 5′ end of transcripts and correlate with higher ribosome density in the 5′-UTR — a finding that hints at a functional role for m5C in regulating mRNA translation.
UBS-seq vs. Conventional Bisulfite Sequencing
| Feature | Conventional BS-seqZymo EZ DNA Methylation-Gold | UBS-seq |
|---|---|---|
| Reaction time | ~160 minutes (10 min + 150 min) | ~9–10 minutes |
| DNA degradation | Severe | Reduced |
| 4mC-to-U conversion | ~50% | Near-quantitative |
| Background on λ-DNA | Baseline | >13-fold lower |
| Single-cell input | Limited, high background | Yes, ~20-fold lower background |
| RNA m5C in structured regions | High false positives | Low background, high sensitivity |
Why This Matters Beyond the Lab
DNA methylation is one of the most widely used epigenetic biomarkers in cancer diagnostics, prenatal testing, and forensic and cfDNA-based liquid biopsy applications. Every one of those applications is bottlenecked by the same problem: bisulfite conversion is slow, damages DNA, and can distort the very methylation signal it’s trying to measure — especially for low-input samples. By showing that ultrafast, high-concentration bisulfite chemistry can solve all of these problems simultaneously, this paper provides a practical foundation for faster, more accurate, and more sample-efficient methylation workflows across both DNA and RNA epigenetics research.
Read the Full Study
This summary covers the highlights, but the original paper includes the full experimental methodology, additional supporting data (including comparisons across GC content, genome coverage, and reproducibility across replicates), and complete statistical analysis.
Original research
Dai, Q., Ye, C., Irkliyenko, I. et al. “Ultrafast bisulfite sequencing detection of 5-methylcytosine in DNA and RNA.” Nature Biotechnology 42, 1559–1570 (2024).
From Academic Discovery to the Bench: SuperMethyl™ Fast
The ultrafast bisulfite chemistry described in this paper didn’t stay in the lab. It has since been further optimized and developed into a commercially available kit: the SuperMethyl™ Fast Bisulfite Conversion Kit from Ellis Bio.
SuperMethyl™ Fast brings this ultrafast bisulfite technology to any lab running methylation workflows, offering:
- A 35-minute total protocol — the fastest bisulfite conversion workflow on the market
- >99.5% conversion efficiency with strong methylation protection
- Compatibility with 10 ng – 2 µg of purified DNA, including gDNA, cfDNA, and FFPE samples
- Compatibility with leading NGS library prep workflows, including KAPA (Roche) and xGen Methyl-Seq (IDT) kits
Try it in your workflow
Ultrafast bisulfite conversion, at your bench
If your research involves DNA methylation profiling, cfDNA biomarker discovery, or NGS-based epigenomics — and you’re working around the slow turnaround and DNA damage of conventional kits — it’s worth seeing how this chemistry performs on your own samples.
Learn more about SuperMethyl™ FastFrequently Asked Questions
What is UBS-seq?
UBS-seq (ultrafast bisulfite sequencing) is a DNA/RNA methylation sequencing method that uses high-concentration ammonium bisulfite reagents and elevated temperature to complete cytosine-to-uracil conversion in minutes instead of hours, reducing DNA/RNA damage and background noise compared with conventional bisulfite sequencing.
How much faster is UBS-seq than conventional bisulfite sequencing?
The core chemical bisulfite conversion is roughly 20 times faster — about 7 minutes versus roughly 160 minutes for the conventional protocol.
Can UBS-seq be used on very small DNA samples, like single cells or cfDNA?
Yes. The paper demonstrates successful library construction from as few as 1–100 mouse embryonic stem cells and from 10 ng of human plasma cfDNA, with substantially lower background than conventional bisulfite sequencing at these low inputs.
Does UBS-seq work for RNA methylation (m5C), not just DNA?
Yes. A modified UBS-seq recipe accurately maps m5C in RNA, including in highly structured RNAs like tRNA and rRNA, and was used to identify thousands of m5C sites in human mRNA. However, commercial kits for RNA are not yet available.
Is the UBS-seq method available as a commercial kit?
Yes. The underlying ultrafast bisulfite chemistry has been further optimized and is available commercially as the SuperMethyl™ Fast Bisulfite Conversion Kit for DNA from Ellis Bio.
How does the cost of the SuperMethyl™ Fast kit compare with conventional bisulfite conversion kits?
At less than $4 per reaction, the SuperMethyl™ Fast 50-reaction kit is the lowest-cost bisulfite conversion kit on the market.