Traditional View of Snornas

Small nucleolar RNAs are small, noncoding RNAs. Based on their sequence, they can be subdivided into C/D and H/ACA snoRNAs. C/D box snoRNAs have C and D boxes as characteristic sequence elements that help form the snoRNA particle, or snoRNP. Small nucleolar RNAs reside in introns from which they are released during pre-mRNA processing of the hosting gene. During the splicing reaction, the intron is released as a lariat structure that contains a 2 to 5 phosphodiester bond at the adenosine branch point. The lariat is opened by a debranching enzyme, and the intron is typically rapidly removed by nuclease action. If the intron contains snoRNAs, proteins associate with the snoRNA sequences and prevent their further degradation. As a result, the snoRNA that "resides" in an intron is released as a snoRNP.

A major function attributed to C/D box snoRNAs is their guiding of 2 -O-methylation in ribosomal, transfer, and snRNAs. The guiding activity of the snoRNAs is achieved by the formation of a specific RNA:RNA duplex between the snoRNA and its target. Most snoRNAs contain two regions to interact with other RNAs, the antisense boxes. Each antisense box exhibits sequence complementarity to its target and forms a short, transient double strand with it. On the target RNA, the nucleotide base pairing with the snoRNA nucleotide positioned five nucleotides downstream of the snoRNA D box is methylated on the 2 -O-hydroxyl group (reviewed in Matera et al. 2007). Several snoRNAs show complementarity towards pre-rRNA, but the rRNA is not 2 -O-methylated at the predicted positions (Steitz and Tycowski 1995). Recently, numerous C/D box snoRNAs were discovered that show no sequence complementarity to other RNAs, suggesting that C/D box snoRNAs might have function other than 2' -O-methylation (Filipowicz and Pogacic 2002). Furthermore, bioinformatics analysis of high-throughput sequencing data provided evidence for shorter forms of snoRNAs, suggesting that snoRNAs could be precursors for miRNA-like nuclear RNAs (Taft et al. 2009; Scott et al. 2009).

Defeat Drugs and Live Free

Defeat Drugs and Live Free

Being addicted to drugs is a complicated matter condition that's been specified as a disorder that evidences in the obsessional thinking about and utilization of drugs. It's a matter that might continue to get worse and become disastrous and deadly if left untreated.

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