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pre-mRNA Processing

pre-mRNA Processing

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl guanosine). This 5’ cap helps the...

Pre-mRNA Processing: Modification of pre-mRNA Ends

Pre-mRNA Processing: Modification of pre-mRNA Ends

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a cap to the 5' end of the growing transcript. In this process, a 5' phosphate is replaced by modified guanosine that has a methyl group attached (7-methyl guanosine). This 5' cap helps the cell...

Transfer RNA Synthesis

Transfer RNA Synthesis

One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...

Eukaryotic RNA Polymerases

Eukaryotic RNA Polymerases

RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional similarities. Among the three eukaryotic RNAPs, RNA Polymerase II is most similar to bacterial RNAP in terms of both structural organization and folding topologies of the enzyme subunits. However, these similarities are not reflected in their mechanism of action.
All three eukaryotic RNAPs require specific transcription factors, of which the...

Ribosomal RNA Synthesis

Ribosomal RNA Synthesis

Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal components occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...

Transcription

Transcription

Overview
Transcription is the process of synthesizing RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. Additionally, many other proteins and regulatory sequences are involved in the proper synthesis of messenger RNA (mRNA). Regulation of transcription is responsible for the differentiation of all the different types of cells and often for the proper cellular response to environmental signals.
Transcription Can Produce Different Kinds...

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Updated: Jul 7, 2026

A Rapid High-throughput Method for Mapping Ribonucleoproteins (RNPs) on Human pre-mRNA

A Rapid High-throughput Method for Mapping Ribonucleoproteins (RNPs) on Human pre-mRNA

Published on: December 2, 2009

Preparation of poly(A)+ RNA.

¹Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA.

Current Protocols in Molecular Biology

|February 12, 2008

Summary

Poly(A) selection enriches messenger RNA (mRNA) for cDNA library construction and analysis of low-abundance messages. This method isolates poly(A)+ RNA from total RNA using oligo(dT) cellulose.

Area of Science:

Molecular Biology
Biochemistry
RNA Biology

Background:

Most messenger RNAs (mRNAs) possess a poly(A) tail, a feature absent in structural RNAs.
Polyadenylation is crucial for mRNA stability, translation, and processing.
Low-abundance mRNAs are challenging to analyze using standard techniques like S1 analysis.

Purpose of the Study:

To describe a protocol for the selective enrichment of poly(A)-containing RNA (poly(A)+ RNA).
To facilitate the construction of complementary DNA (cDNA) libraries.
To enable the analysis of low-abundance messenger RNA populations.

Main Methods:

Total RNA is denatured to expose the poly(A) tails.
Poly(A)+ RNA is isolated using oligo(dT) cellulose chromatography.

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Last Updated: Jul 7, 2026

A Rapid High-throughput Method for Mapping Ribonucleoproteins (RNPs) on Human pre-mRNA

A Rapid High-throughput Method for Mapping Ribonucleoproteins (RNPs) on Human pre-mRNA

Published on: December 2, 2009

Transcriptome Analysis of Single Cells

Transcriptome Analysis of Single Cells

Published on: April 25, 2011

Single Read and Paired End mRNA-Seq Illumina Libraries from 10 Nanograms Total RNA

Single Read and Paired End mRNA-Seq Illumina Libraries from 10 Nanograms Total RNA

Published on: October 27, 2011

The binding of poly(A)+ RNA to oligo(dT) cellulose is dependent on salt concentration.

Main Results:

The protocol effectively separates poly(A)+ RNA from ribosomal RNA (rRNA) and transfer RNA (tRNA).
Repeated column passes can further purify the poly(A)+ RNA fraction.
Enriched poly(A)+ RNA is suitable for downstream applications like cDNA synthesis and S1 analysis.

Conclusions:

Poly(A) selection is an essential technique for enriching messenger RNA.
This method significantly improves the efficiency of cDNA library construction.
The protocol allows for the detection and analysis of low-level mRNA transcripts.