Difference Between snRNA and snRNP

The key difference between snRNA and snRNP is that snRNAs are small nuclear RNA molecules while snRNPs or small nuclear ribonucleoproteins are small nuclear RNA molecules with proteins.

snRNAs are non-coding, biologically active small RNA molecules with an average size of 150 nucleotides. They are usually present in association with proteins as snRNPs in the natural state. Hence, snRNPs are small nuclear RNA with several snRNP-specific proteins. snRNPs are involved in mediating or regulating post-translational RNA-processing events such as splicing, etc. Both snRNA and snRNP are found in the nucleus of eukaryotic cells.

CONTENTS

1. Overview and Key Difference
2. What is snRNA
3. What is snRNP
4. Similarities Between snRNA and snRNP
5. Side by Side Comparison – snRNA vs snRNP in Tabular Form
6. Summary

What is snRNA?

snRNA stands for small nuclear RNA. They are small nuclear RNA molecules found within the splicing speckles and Cajal bodies of the cell nucleus in eukaryotic cells. An snRNA molecule has an average length of 150 nucleotides. These snRNAs are transcribed by pol II and pol III. The main function of snRNA is the processing of pre-messenger RNA (hnRNA) in the nucleus. They are mainly involved in mediating or regulating post-translational RNA-processing events such as splicing. Due to snRNAs action, precise alignment and correct excision of introns take place. Moreover, snRNAs participate in the regulation of transcription factors (7SK RNA) or RNA polymerase II (B2 RNA) and maintaining telomeres.

snRNAs are non-coding RNAs. They belong to a class of highly abundant biologically active RNA localized in the nucleus. They are always associated with protein molecules and exist as small nuclear ribonucleoproteins (snRNP). There are two main types of snRNAs as Sm-class snRNA and Lsm-class snRNA. U1, U2, U4, U4atac, U5, U7, U11, and U12 are Sm-class snRNA while U6 and U6atac are Lsm-class snRNA.

What is snRNP?

snRNP is a small nuclear RNA molecule combined with proteins. Generally, each snRNP contains a single snRNA and many protein molecules. Therefore, snRNPs are small nuclear RNA molecules and proteins. snRNPs, together with many other additional proteins, form the complex called spliceosome where RNA splicing takes place. snRNPs need both the RNA part and the protein part to splice out introns. The RNA component is responsible for the endonuclease cuts since it has enzymatic activity. There are different types of snRNPs, and they cut at different locations.

In addition to splicing, snRNPs participate in nuclear maturation of primary transcripts in mRNAs, gene expression regulation, splice donor in non-canonical systems and in 3′-end processing of replication-dependent histone mRNAs. There are two special groups of snRNPs as small nucleolar RNPs (snoRNPs) and small Cajal-body RNPs (scaRNPs).

What are the Similarities Between snRNA and snRNP?

• Both snRNA and snRNP have small nuclear RNA molecules.
• snRNAs combine with proteins to make snRNPs.
• Each snRNP contains a single snRNA.
• Both snRNA and snRNP are found in the nucleus of eukaryotic cells.

What is the Difference Between snRNA and snRNP?

snRNA is a small non-coding RNA molecule localized within the eukaryotic cell nucleus while snRNP is a complex of a single snRNA and snRNP specific proteins. snRNPS are small nuclear ribonucleoprotein particles. snRNA is just a small RNA molecule while snRNP is a complex of snRNA molecule and tightly bound proteins. So, this is the key difference between snRNA and snRNP.

Below infographic shows the differences between snRNA and snRNP in tabular form.

Summary – snRNA vs snRNP

snRNA is a class of non-coding small nuclear RNA localized in the eukaryotic nucleus. They fulfil important functions related to intron splicing and other RNA processing. In the natural state, snRNA is associated with proteins and exists as small nuclear ribonucleoprotein particles (snRNPs). snRNPs, together with many other proteins, are involved in the formation of the spliceosome complex in order to carry out RNA splicing. Thus, this summarizes the difference between snRNA and snRNP.

Reference:

1. Stone, Lauren B, and Kasandra J Riley. “Small Nuclear Ribonucleoproteins (SnRNPs).” Wiley Online Library, American Cancer Society, 15 Aug. 2014, onlinelibrary.wiley.com/doi/abs/10.1002/9780470015902.a0005038.
2. “Small Nuclear RNA.”ScienceDirect Topics, Available here.

Image Courtesy:

1. “RF00003” – from the Rfam database (Public Domain) via Commons Wikimedia
2. “Spliceosome ball cycle new2” By JBrain – (CC BY-SA 2.0 de) via Commons Wikimedia