Ribosomes are macromolecular machines, found within all cells, that perform biological protein synthesis. Ribosomes link amino acids together in the order specified by the codons of messenger RNA (mRNA) molecules to form polypeptide chains. Ribosomes consist of two major components: the small and large ribosomal subunits. Each subunit consists of one or more ribosomal RNA (rRNA) molecules and many ribosomal proteins. The ribosomes and associated molecules are also known as the translational apparatus.
Cajal bodies (CBs) also coiled bodies, are spherical nuclear bodies of 0.3–1.0 µm in diameter found in the nucleus of proliferative cells like embryonic cells and tumor cells, or metabolically active cells like neurons. CBs are membrane-less organelles and largely consist of proteins and RNA. They were first reported by Santiago Ramón y Cajal in 1903, who called them nucleolar accessory bodies due to their association with the nucleoli in neuronal cells. They were rediscovered with the use of the electron microscope (EM) and named coiled bodies, according to their appearance as coiled threads on EM images, and later renamed after their discoverer. Research on CBs was accelerated after discovery and cloning of the marker protein p80/Coilin. CBs have been implicated in RNA-related metabolic processes such as the biogenesis, maturation and recycling of snRNPs, histone mRNA processing and telomere maintenance. CBs assemble RNA which is used by telomerase to add nucleotides to the ends of telomeres.
Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal DNA (rDNA) and then bound to ribosomal proteins to form small and large ribosome subunits. rRNA is the physical and mechanical factor of the ribosome that forces transfer RNA (tRNA) and messenger RNA (mRNA) to process and translate the latter into proteins. Ribosomal RNA is the predominant form of RNA found in most cells; it makes up about 80% of cellular RNA despite never being translated into proteins itself. Ribosomes are composed of approximately 60% rRNA and 40% ribosomal proteins by mass.
Nucleoproteins are proteins conjugated with nucleic acids. Typical nucleoproteins include ribosomes, nucleosomes and viral nucleocapsid proteins.
Small nuclear RNA (snRNA) is a class of small RNA molecules that are found within the splicing speckles and Cajal bodies of the cell nucleus in eukaryotic cells. The length of an average snRNA is approximately 150 nucleotides. They are transcribed by either RNA polymerase II or RNA polymerase III. Their primary function is in the processing of pre-messenger RNA (hnRNA) in the nucleus. They have also been shown to aid in the regulation of transcription factors or RNA polymerase II, and maintaining the telomeres.
Heterogeneous nuclear ribonucleoproteins (hnRNPs) are complexes of RNA and protein present in the cell nucleus during gene transcription and subsequent post-transcriptional modification of the newly synthesized RNA (pre-mRNA). The presence of the proteins bound to a pre-mRNA molecule serves as a signal that the pre-mRNA is not yet fully processed and therefore not ready for export to the cytoplasm. Since most mature RNA is exported from the nucleus relatively quickly, most RNA-binding protein in the nucleus exist as heterogeneous ribonucleoprotein particles. After splicing has occurred, the proteins remain bound to spliced introns and target them for degradation.
The 23S rRNA is a 2,904 nucleotide long component of the large subunit (50S) of the bacterial/archean ribosome and makes up the peptidyl transferase center (PTC). The 23S rRNA is divided into six secondary structural domains titled I-VI, with the corresponding 5S rRNA being considered domain VII. The ribosomal peptidyl transferase activity resides in domain V of this rRNA, which is also the most common binding site for antibiotics that inhibit translation, making it a target for ribosomal engineering. A well-known member of this antibiotic class, chloramphenicol, acts by inhibiting peptide bond formation, with recent 3D-structural studies showing two different binding sites depending on the species of ribosome. Numerous mutations in domains of the 23S rRNA with Peptidyl transferase activity have resulted in antibiotic resistance. 23S rRNA genes typically have higher sequence variations, including insertions and/or deletions, compared to other rRNAs.
Nucleolin is a protein that in humans is encoded by the NCL gene.
Telomerase RNA component, also known as TR, TER or TERC, is an ncRNA found in eukaryotes that is a component of telomerase, the enzyme used to extend telomeres. TERC serves as a template for telomere replication by telomerase. Telomerase RNAs differ greatly in sequence and structure between vertebrates, ciliates and yeasts, but they share a 5' pseudoknot structure close to the template sequence. The vertebrate telomerase RNAs have a 3' H/ACA snoRNA-like domain.
H/ACA ribonucleoprotein complex subunit 4 is a protein that in humans is encoded by the gene DKC1.
Telomerase protein component 1 is an enzyme that in humans is encoded by the TEP1 gene.
The vault or vault cytoplasmic ribonucleoprotein is a eukaryotic organelle whose function is not yet fully understood. Discovered and isolated by Nancy Kedersha and Leonard Rome in 1986, vaults are cytoplasmic organelles which, when negative-stained and viewed under an electron microscope, resemble the arches of a cathedral's vaulted ceiling, with 39-fold symmetry. They are present in many types of eukaryotic cells, and appear to be highly conserved among eukaryotes.
EF-G is a prokaryotic elongation factor involved in protein translation. As a GTPase, EF-G catalyzes the movement (translocation) of transfer RNA (tRNA) and messenger RNA (mRNA) through the ribosome.
Numerous key discoveries in biology have emerged from studies of RNA, including seminal work in the fields of biochemistry, genetics, microbiology, molecular biology, molecular evolution and structural biology. As of 2010, 30 scientists have been awarded Nobel Prizes for experimental work that includes studies of RNA. Specific discoveries of high biological significance are discussed in this article.
In molecular biology, the single-domain protein SUI1 is a translation initiation factor often found in the fungus, Saccharomyces cerevisiae but it is also found in other eukaryotes and prokaryotes as well as archaea. It is otherwise known as Eukaryotic translation initiation factor 1 (eIF1) in eukaryotes or YciH in bacteria.
The E-site is the third and final binding site for t-RNA in the ribosome during translation, a part of protein synthesis. The "E" stands for exit, and is accompanied by the P-site which is the second binding site, and the A-site (aminoacyl), which is the first binding site. It is involved in cellular processes.
William Henry Andrews is an American molecular biologist and gerontologist whose career has centered on searching for a cure for human aging. Andrews is the founder and president of the biotechnology company Sierra Sciences. In the 1990s, he led the team at Geron Corporation that was the first to successfully identify the genes for human enzyme telomerase. This enzyme is responsible for preventing telomeres from shortening in human primordial germ cells.
16S rRNA (guanine966-N2)-methyltransferase (EC 2.1.1.171, yhhF (gene), rsmD (gene), m2G966 methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:16S rRNA (guanine966-N2)-methyltransferase. This enzyme catalyses the following chemical reaction
23S rRNA (guanine2445-N2)-methyltransferase (EC 2.1.1.173, ycbY (gene), rlmL (gene)) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (guanine2445-N2)-methyltransferase. This enzyme catalyses the following chemical reaction
23S rRNA (guanine1835-N2)-methyltransferase (EC 2.1.1.174, ygjO (gene), rlmG (gene), ribosomal RNA large subunit methyltransferase G) is an enzyme with systematic name S-adenosyl-L-methionine:23S rRNA (guanine1835-N2)-methyltransferase. This enzyme catalyses the following chemical reaction
