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Molecule is being transported from the nucleus to the cytosol. As its 5ʹ end emerges from a nuclear pore, the mRNA is met by a ribosome, which begins to translate it. As translation proceeds, the exon junction complexes (EJCs) that are bound to the mRNA at each splice site are displaced by the moving ribosome. The normal stop...
Although it may seem at first counterintuitive, the way a gene is packaged into chromatin can affect how the RNA transcript of that gene is ultimately spliced. Nucleosomes tend to be positioned over exons (which are, on average, close to the length of DNA in a nucleosome), and it has been proposed that these act as “speed bumps,”...
Schematic illustration of an export-ready mRNA molecule and its transport through the nuclear pore. As indicated, some proteins travel with the mRNA as it moves through the pore, whereas others remain in the nucleus. The nuclear export receptor for mRNAs is a complex of proteins that binds to an mRNA molecule once it has been correctly spliced and...
Schematic illustration showing how the clamp (with red and yellow subunits) is loaded onto DNA to serve as a tether for a moving DNA polymerase molecule. The structure of the clamp loader (dark green) resembles a screw nut, with its threads matching the grooves of double-stranded DNA. The loader binds to a free clamp molecule, forcing a gap...
DNA polymerase performs the first proofreading step just before a new nucleotide is covalently added to the growing chain. Our knowledge of this mechanism comes from studies of several different DNA polymerases, including one produced by a bacterial virus, T7, that replicates inside E. coli. The correct nucleotide has a higher affinity for the moving polymerase than does...
DNA templating is the mechanism the cell uses to copy the nucleotide sequence of one DNA strand into a complementary DNA sequence This process requires the separation of the DNA helix into two template strands, and entails the recognition of each nucleotide in the DNA template strands by a free (unpolymerized) complementary nucleotide. During DNA replication inside a...
Nucleosomes carrying histone variants have a distinctive character and are thought to be able to produce marks in chromatin that are unusually long-lasting. An important example is seen in the formation and inheritance of the specialized chromatin structure at the centromere, the region of each chromosome required for attachment to the mitotic spindle and orderly segregation of the...
Each chromosome in a eukaryotic cell consists of a single, enormously long linear DNA molecule along with the proteins that fold and pack the fine DNA thread into a more compact structure. In addition to the proteins involved in packaging, chromosomes are also associated with many other proteins (as well as numerous RNA molecules). These are required for...
The proteins that bind to the DNA to form eukaryotic chromosomes are traditionally divided into two classes: the histones and the non-histone chromosomal proteins, each contributing about the same mass to a chromosome as the DNA. The complex of both classes of protein with the nuclear DNA of eukaryotic cells is known as chromatin Nucleosomes as seen in the...
A deoxyribonucleic acid (DNA) molecule consists of two long polynucleotide chains composed of four types of nucleotide subunits. Each of these chains is known as a DNA chain, or a DNA strand. The chains run antiparallel to each other, and hydrogen bonds between the base portions of the nucleotides hold the two chains together DOUBLE HELIX The three-dimensional...
Nucleosomes : Basic Unit of Eukaryotic Chromosome Structure
DNA Replication : The Mehcanism
DNA Replication : The Regulated Sliding Clamp
DNA : The Structure and Function
DNA to RNA : RNA Splicing
Centromere : A model for the structure of a Simple
Chromosomal : Packaged into a Set of Chromosomes
DNA to RNA : Transcription and Translation
RNA to Protein : Degradation and Splicing
DNA Replication : The Introduction
The proteins that bind to the DNA to form eukaryotic chromosomes are traditionally divided into two classes: the histones and the non-his...
