Small Nuclear RNA 

"Small nuclear ribonucleic acid (snRNA), also commonly referred to as U-RNA, is a class of small RNA molecules that are found within the nucleus of eukaryotic cells. The length of the an average snRNA is approximately 150 nucleotides. They are transcribed by either RNA polymerase II or RNA polymerase III, and studies have shown that their primary function is in the processing of pre-mRNA (hnRNA) in the nucleus. They have also been shown to aide in the regulation of transcription factors (7SK RNA) or RNA polymerase II (B2 RNA), and maintaining the telomeres."

"snRNA are always associated with a set of specific proteins, and the complexes are referred to as small nuclear ribonucleoproteins (snRNP) often pronounced "snurps". Each snRNP particle is composed of several Sm proteins, the snRNA component, and snRNP specific proteins. The most common snRNA components of these complexes are known, respectively, as: U1 snRNA, U2 snRNA, U4 snRNA, U5 snRNA, and U6 snRNA. Their nomenclature derives from their high uridine content."

"snRNAs were discovered by accident during a gel electrophoresis experiment in 1966. An unexpected type of RNA was found in the gel and investigated. Later analysis has shown that these RNA were high in uridylate and were established in the nucleus."