Small nuclear ribonucleic acid (snRNA) is a class of small RNA molecules involved in splicing pre-messenger RNA in eukaryotic cells. SnRNAs, categorized into sm-class and lsm-class, work with specific proteins to form small nuclear ribonucleoproteins (snRNPs) that are crucial for the spliceosome complex responsible for RNA maturation. The spliceosome, composed of snRNAs and numerous proteins, facilitates the removal of introns and ligates exons to create mature mRNA.

1. Gupta College Of Technological Sciences
Pharmaceutical Biochemistry
Name:-Vicktor Ghosh
Roll:-181240210105
Session:-2nd sem, 1st year
Topic:-SnRNA
Yeae:-2018-2019

2. SnRNA
Small nuclear ribonucleic acid (snRNA) is a class of small RNA molecules that
are found within the splicing speckles and Cajal bodies of the cell nucleus
ineukaryotic cells. The length of an averagesnRNA is approximately 150
nucleotides.They are transcribed by either RNApolymerase II or RNA
polymerase III.Their primary function is in the processingof pre-messenger
RNA (hnRNA) in the nucleus. snRNA are always associated with a set of
specific proteins, and the complexes are referred to as small
nuclearribonucleoproteins (snRNP, often pronounced "snurps").

3. SnRNA
Each snRNP particle is composed of a snRNA component and several
snRNP-specific proteins. The most common snRNA components of these
complexes are known, respectively, as: U1, U2, U3, U4, U5 and U6
spleciosomal RNA.Their nomenclature derives from high Uridine content.
Classes:-snRNA are often divided into two classes based upon both common
sequence features as well as associated protein. factors such as the RNA-
binding LSm proteins.The first class, known as Sm-class snRNA, is more
widely studied and consists of U1,U2, U4, U4atac, U5, U7, U11, and U12.

4. snRNA
Classes:
Sm-class snRNA are transcribed by RNA polymerase II. The pre-snRNA are
transcribed and receive the usual 7-methylguanosine five prime cap in the
nucleus. They are then exported to the cytoplasm through nuclear pores for
further processing. All of these uridine-rich snRNA, with the exception of U7,
form the core of the spliceosome. Splicing, or the removal of introns, is a major
aspect of post-transcriptional modification, and takes place only in the nucleus
of eukaryotes.
The second class, known as Lsm-class snRNA, consists of U6 and U6atac.
Lsm-classs sRNAs are transcribed by RNA polymerase III and never leave the
nucleus.

5. snRNA
In spleciosome:-
Spliceosomes catalyse splicing, an integral step in eukaryotic precursor
Messenger RNA maturation. The spliceosome is a large, protein-
RNAcomplex that consists of five small nuclear RNAs (U1, U2, U4, U5,
and U6) and over 150 proteins. The snRNAs, along with their associated
proteins, form ribonucleoprotein complexes (snRNPs), which bind to
specific sequences on the pre-mRNA substrate.This intricate process results
in two sequential transesterification reactions. These reactions will produce a
free lariat intron and ligate two exons to form a maturemRNA.

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