Enrichment of mRNA and Bisulfite-mRNA Library Preparation for Next-Generation Sequencing

Summary

This protocol provides an easy-to-follow workflow to conduct poly(A) RNA purification, bisulfite conversion, and library preparation using standardized equipment for a biological sample of interest.

Abstract

RNA post-transcriptional modifications in various types of RNA transcripts are associated with diverse RNA regulation in eukaryotic cells. Aberrant RNA 5-methylcytosine modifications and the dysregulated expression of RNA methyltransferases have been shown to be associated with various diseases, including cancers. Transcriptome-wide bisulfite-sequencing was developed to characterize the positions and the quantitative cytosine methylation levels in the bisulfite-converted RNA at the base-pair resolution. Herein, this protocol presents the procedures of two rounds of poly(A) RNA purification, three cycles of bisulfite reaction, and library preparation in detail to allow the transcriptome-wide mapping of mRNA 5-methylcytosine modification sites. The assessment of RNA quantity and quality after the main reaction is essential to monitor RNA integrity and is a critical step for ensuring high-quality sequencing libraries. Ideally, the procedures can be completed within three days. With this protocol, using high-quality total RNA as the input can practically build up robust bisulfite-mRNA libraries for next-generation sequencing from the sample of interest.

Introduction

Among over 150 types of post-transcriptional modifications¹, 5-methylcytosine (m⁵C) modification has been identified in various types of RNAs, including ribosomal RNA, transfer RNA, messenger RNA, micro RNA, long non-coding RNA, vault RNA, enhancer RNA, and small cajal body-specific RNAs². The RNA m⁵C is associated with diverse biological and pathological mechanisms such as regulating plant root development³, viral gene expression⁴, and cancer progression⁵. The aim of this protocol is to provide streamlined pipelines to characte....

Protocol

1. Poly(A) RNA purification

NOTE: Use the total RNA treated with DNase I and examine the total RNA quality and integrity by capillary or conventional gel electrophoresis assessment before proceeding to poly(A) RNA purification. Investigators should be able to identify the 28S and 18S rRNA ribosomal bands in the high molecular weight field and the 5.8S rRNA band in the low molecular weight field without any significant smear bands in the electropherogram. The purification steps e.......

Discussion

In this protocol, a detailed pipeline of poly(A) enrichment, bisulfite conversion, and library preparation was achieved by utilizing standardized components. Further sequencing analysis provided the identification of mRNA 5-methylcytosine in samples of interest.

The critical step is the quality of starting material-total RNA-since the degradation of RNA would impact the recovery rate of poly(A) RNA purification. The sample should be carefully handled and RNase contamination avoided before cond.......

Materials

Name	Company	Catalog Number	Comments
Agilent 2100 Electrophoresis Bioanalyzer System	Agilent, Santa Clara, CA		RNA quality detection
AMpure XP beads	Beckman Coulter	A63881	purify DNA
Bioanalyzer DNA high sensitivity kit	Agilent, Santa Clara, CA	5067-4626	DNA quality dection
Bioanalyzer RNA 6000 Pico kit	Agilent, Santa Clara, CA	5067-1513	RNA quality dection
DiaMag02 - magnetic rack	Diagenode, Denville, NJ	B04000001	assist library preparation
DiaMag1.5 - magnetic rack	Diagenode, Denville, NJ	B04000003	assist poly(A) RNA purificaion
Dynabeads mRNA DIRECT purification kit	Thermo Fisher Scientific, Waltham, MA	61011	poly(A) RNA purificaion; Wash Buffer 1 and Wash Buffer 2
Ethanol	J.T.Baker	64-17-5
EZ RNA methylation kit	Zymo, Irvine, CA	R5002	bisulfite treatment
Firefly luciferase mRNA	Promega, Madison, WI, USA	L4561	spike in control seqeunce
KAPA Library Quantification Kits	Roche, Switzerland	KK4824	library quantification
Nanodrop spectrophotometer	Thermo Fisher Scientific, Waltham, MA		Total RNA quantity detection
NEBNext multiplex Oligos for illumina (index Primer set1)	New England Biolabs, Ipswich, MA	E7335S	library preparation
NEBNext Ultra Directional RNA Library Prep Kit for Illumina	New England Biolabs, Ipswich, MA	E7760S	library preparation
Nuclease-free Water	Thermo Fisher Scientific	AM9932
P2 pipetman	Thermo Fisher Scientific, Waltham, MA	4641010
Qubit 2.0 fluorometer	Thermo Fisher Scientific, Waltham, MA		RNA quantity detection
Qubit dsDNA HS Assay Kit	Thermo Fisher Scientific, Waltham, MA	Q32854	DNA quantity detection
Qubit RNA HS Assay Kit	Thermo Fisher Scientific, Waltham, MA	Q32852	RNA quantity detection