EukaryoteThe eukaryotes constitute the domain of Eukaryota (juːˈkærioʊts,_-əts), organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms are eukaryotes. They constitute a major group of life forms, alongside the two groups of prokaryotes, the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but due to their generally much larger size, their collective global biomass is much larger than that of prokaryotes.
Transcription factor II BTranscription factor II B (TFIIB) is a general transcription factor that is involved in the formation of the RNA polymerase II preinitiation complex (PIC) and aids in stimulating transcription initiation. TFIIB is localised to the nucleus and provides a platform for PIC formation by binding and stabilising the DNA-TBP (TATA-binding protein) complex and by recruiting RNA polymerase II and other transcription factors. It is encoded by the gene, and is homologous to archaeal transcription factor B and analogous to bacterial sigma factors.
Transcription factorIn molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The function of TFs is to regulate—turn on and off—genes in order to make sure that they are expressed in the desired cells at the right time and in the right amount throughout the life of the cell and the organism.
Protein foldingProtein folding is the physical process where a protein chain is translated into its native three-dimensional structure, typically a "folded" conformation, by which the protein becomes biologically functional. Via an expeditious and reproducible process, a polypeptide folds into its characteristic three-dimensional structure from a random coil. Each protein exists first as an unfolded polypeptide or random coil after being translated from a sequence of mRNA into a linear chain of amino acids.
IntronAn intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word intron is derived from the term intragenic region, i.e., a region inside a gene. The term intron refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. The non-intron sequences that become joined by this RNA processing to form the mature RNA are called exons. Introns are found in the genes of most organisms and many viruses and they can be located in both protein-coding genes and genes that function as RNA (noncoding genes).
Membrane proteinMembrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane (integral monotopic). Peripheral membrane proteins are transiently associated with the cell membrane.
Messenger RNAIn molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the process of transcription, where an enzyme (RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA). This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence.
Enhancer (genetics)In genetics, an enhancer is a short (50–1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. Enhancers are cis-acting. They can be located up to 1 Mbp (1,000,000 bp) away from the gene, upstream or downstream from the start site. There are hundreds of thousands of enhancers in the human genome. They are found in both prokaryotes and eukaryotes.
Transcription (biology)Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA (Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA.
RNA splicingRNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing all the introns (non-coding regions of RNA) and splicing back together exons (coding regions). For nuclear-encoded genes, splicing occurs in the nucleus either during or immediately after transcription. For those eukaryotic genes that contain introns, splicing is usually needed to create an mRNA molecule that can be translated into protein.
Cell nucleusThe cell nucleus (; : nuclei) is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and isolates its contents from the cellular cytoplasm; and the nuclear matrix, a network within the nucleus that adds mechanical support.
