Our RNA World @ MHC

Virus-encoded Circular RNAs:  A brand-new class of gene regulators What is a normal shape of general RNAs you have learned about before? Are all types of RNAs linear as we often think? The answer is NO! Different from other members in the RNA-family, circular RNA (circRNA) is a novel class of RNA that is not linear. Instead, it forms a covalently closed continuous loop in which the 3'end and 5'end in an RNA molecule are joined together. In eukaryotes, pre-mRNA goes through processing which the 5'end is capped with 7MetG and the 3'end is added with a lot of adenines. With circRNAs, the absence of the two ends as well as the polyadenylated tail makes circRNAs resistant to degradation and more stable than most linear RNAs in cells. With this distinct shape, circRNAs display many original properties that other RNAs don't have. Therefore, circRNA is one of the most actively fields in RNA-targeted therapeutic treatments of research in recent years. C...

Signal Recognition Particle: the RNA key to protein secretion  Proteins are found everywhere within a cell. Many localize in the cell membranes, where they play crucial roles in everything from signal reception and transduction to ion balance and ATP synthesis. But how do new proteins get incorporated into the membranes from their origin of translation in the cytosol? One of the ways that the cell does this is through the use of co-translational systems that enable a protein to be translated by a ribosome while the unfolded polypeptide chain is thread through a channel protein in a membrane. There are a variety of systems that perform this function, but the most conserved system found in prokaryotes and eukaryotes is SRP-RNC-Sec61/SecYEG. The SRP-RNC-Sec61/SecYEG pathway involves the use of signal recognition particle (SRP), signal receptor (SR), ribosome-nascent chain complex (RNC), and the Sec61 (or SecYEG in eukaryotes) membrane channel protein. The RNC refers to a rib...

The GlmS   Riboswitch: A very unique addition to the catalytic RNA family! Figure 1. Riboswitch folding! (People in White Coats) We have all heard at some point that our genetic information is encoded in our DNA. Perhaps you have also heard that RNA is transcribed from DNA, and that proteins are synthesized from the information carried by RNA. This is known as the Central Dogma of Molecular Biology. From the Central Dogma, one would think that RNA only serves as a messenger, relaying instructions from DNA to protein, but that is not the case! RNA molecules are capable of participating in a wide array of reactions! They can even perform catalysis—previously thought to be exclusively performed by proteins. These catalytic RNA molecules have been dubbed “ribozymes.” Another interesting set of RNA molecules are the riboswitches. Riboswitches regulate gene expression. They are found in the sequence immediately prior to the gene that they regulated, and, ...