RNA and Non-Coding RNA 2025 PDF

WE MAKE DOCTORS RNA structure and function. Non coding RNAs. Ana Gabriela Colima Fausto, PhD Learning objectives Identify the characteristics of the RNA molecule and its types: messenger, transfer and ribosomal Outline the main characteristics of non-coding RNA and its classificatio...

WE MAKE DOCTORS RNA structure and function. Non coding RNAs. Ana Gabriela Colima Fausto, PhD Learning objectives Identify the characteristics of the RNA molecule and its types: messenger, transfer and ribosomal Outline the main characteristics of non-coding RNA and its classification Describe clinical applications of mRNA and non-coding RNAs: Vaccines and Antisense oligonucleotides RNA Essential and polymeric molecule Expression of genes Like DNA, RNA is assembled as a chain of nucleotides, but unlike DNA it is more often found in nature as a single-strand folded onto itself RNA Several distinct types of RNA are known: ribosomal (rRNA), transfer (tRNA), messenger (mRNA), each with its own distinctive structure and function. tRNA and rRNA are transcribed but not translated (ncRNAs). There are additional small RNAs that are also noncoding, like the ones in the nucleolus (snoRNAs) nucleus (snRNA) and cytoplasm (miRNA) that perform specialized functions. RNA STRCTURE The chemical structure of RNA is very similar to that of DNA the RNA is a single-stranded molecule RNA contains ribose ( hidroxyl groups- less stable-hydrolisis) DNA thymine vs RNA uracil. Hydroxyl group at the 2' position of the ribose sugar. The presence of this functional group causes the helix to mostly take the A-form geometry mRNA mRNA carries genetic information from DNA to cytosol for translation. About 5% of the total RNA within a cell is mRNA. It is the most heterogeneous in terms of size and carries specific information necessary for the synthesis of different proteins tRNA tRNA is the smallest of the three RNAs. It carries the appropriate amino acid and provide a mechanism by which nucleotide information can be translated to amino acid information through its anticodon There is one tRNA molecule for each codon tRNA Contains only 80 nucleotides, tRNAs represent approximately 15% of the total RNA of the cell 10-20% of the nucleotides are modified Dihydrouridine, ribothymidine, pseudouridine.  rRNA rRNA accounts for 80% of total RNA in the cell and associates with proteins to form ribosomes. Eukaryotes have several different rRNA molecules: 18S, 28S, 5S, and 5.8S. All ribosomal RNAs are encoded in only 1 single transcript set, 45S. Ribosomes are important during protein synthesis as they contain peptidyl transferase “activity,” an activity catalyzed by ribozymes Non-coding RNA Encoded by genes and are single-stranded. They are 21 to 23 nucleotides in length. These molecules are transcribed but not translated. They function in regulating gene expression by their ability to bind mRNA and to downregulate the gene expression. Non-coding RNAs contribute to diseases such as cancers, autism, Alzheimer among others. Non-coding RNA Translation (tRNA, rRNA) Splicing (snRNA) Gene regulation (miRNA) Genome defense (piRNA) Chromosome structure (Xist)  miRNA MicroRNAs (miRNA) bind to a specific target messenger RNA with a complementary sequence to induce cleavage, or degradation or block translation. miRNAs will pair target mRNAs transcripts through the 3’UTR, leading to gene silencing They repress the initiation step of the translation process, which may be followed by mRNA degradation  Clinical applications ANTISENSE OLIGONUCLEOTIDES Represent an opportunity for strategical intervention to target RNA encoding proteins that are difficult to reach with conventional therapy, or to selectively target non- coding RNAs, specially miRNAs. Polymers consisting of 15–21 nucleotides: single stranded DNA or RNA nucleotide sequences complementary to an endogenous miRNA, double-stranded complexes called short interfering RNA (siRNA) ✓Promote RNA cleavage through the recruitment of endogenous enzymes ✓ Interfere with mRNA translation without promoting the degradation of the target NAME TYPE INDICATION Fomivirsen ASO Cytomegalovirus retinitis Mipomersen ASO Homozygous familial hypercholesterolemia Eteplirsen ASO Duchenne muscular dystrophy Nusinersen ASO Spinal muscular atrophy Patisiran siRNA Human hereditary transthyretin amyloidosis Volanesorsen ASO Familial chylomicronemia syndrome Givosiran siRNA Acute hepatic porphyria  Clinical applications Hepatitis C virus (HCV) infection. NS3 and NS5B siRNAs can inhibit HCV RNA replication and protein expression in Huh- 7 cells  Clinical applications: RNA Vaccines mRNA-based COVID-19 vaccines (Pfizer–BioNTech and Moderna vaccines ) Introduce a short-lived synthetically created fragment of the RNA sequence These mRNA fragments are taken up by dendritic cells through phagocytosis. The dendritic cells use ribosomes to produce the viral antigens that the mRNA encodes. The body degrades the mRNA fragments within a few days of introduction. RNA-based cancer vaccines Designed to express tumor- associated antigens, resulting in the stimulation of T-cell- mediated immune responses Acute myeloid leukemia, brain cancer, colorectal cancer, liver metastases, esophagus cancer, glioblastoma, prostate cancer, and melanoma (RNA-based cancer vaccine candidates) Applied in a therapeutic rather than a prophylactic manner Machado BAS, Hodel KVS, Fonseca LMDS, Mascarenhas LAB, Andrade LPCDS, Rocha VPC, Soares MBP, Berglund P, Duthie MS, Reed SG, Badaró R. The Importance of RNA-Based Vaccines in the Fight against COVID-19: An Overview. Vaccines (Basel). 2021 Nov 17;9(11):1345.  RNA Vaccines against Non-Infectious Diseases RNA-based vaccines also have a great potential to be applied to the treatment and prophylaxis of non- infectious diseases, such as autoimmune and allergic diseases mRNA-based vaccine acts by suppressing antigen- specific immune responses Increase immune cell tolerance and consequently reducing damage without jeopardizing the immune system functions Bibliography Chapter 8 Chandar, Nalini and Viselli, Susan. Lippincott's Illustrated Reviews: Cell and Molecular Biology, 2nd Edition Lippincott Williams & Wilkins, a Wolters Kluwer Health Publication, 2019.