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Poly(A)-specific Ribonuclease
Poly(A)-specific ribonuclease (PARN), also known as polyadenylate-specific ribonuclease or deadenylating nuclease (DAN), is an enzyme that in humans is encoded by the ''PARN'' gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei .... Function Exonucleolytic degradation of the poly(A) tail is often the first step in the decay of eukaryotic mRNAs. The amino acid sequence of poly(A)-specific ribonuclease shows homology to the RNase D family of 3'- exonucleases. The protein appears to be localized in both the nucleus and the cytoplasm. It is not stably associated with polysomes or ribosomal subunits. Hereditary mutations in PARN lead to the bone marrow failure disease dyskeratosis congenita which is caused by defective telomerase RNA processing and degradation in patients. Re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecules known as product (chemistry), products. Almost all metabolism, metabolic processes in the cell (biology), cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme, pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts include Ribozyme, catalytic RNA molecules, also called ribozymes. They are sometimes descr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protein-coding genes and non-coding genes. During gene expression (the synthesis of Gene product, RNA or protein from a gene), DNA is first transcription (biology), copied into RNA. RNA can be non-coding RNA, directly functional or be the intermediate protein biosynthesis, template for the synthesis of a protein. The transmission of genes to an organism's offspring, is the basis of the inheritance of phenotypic traits from one generation to the next. These genes make up different DNA sequences, together called a genotype, that is specific to every given individual, within the gene pool of the population (biology), population of a given species. The genotype, along with environmental and developmental factors, ultimately determines the phenotype ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyadenylation
Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature mRNA for translation. In many bacteria, the poly(A) tail promotes degradation of the mRNA. It, therefore, forms part of the larger process of gene expression. The process of polyadenylation begins as the transcription of a gene terminates. The 3′-most segment of the newly made pre-mRNA is first cleaved off by a set of proteins; these proteins then synthesize the poly(A) tail at the RNA's 3′ end. In some genes these proteins add a poly(A) tail at one of several possible sites. Therefore, polyadenylation can produce more than one transcript from a single gene (alternative polyadenylation), similar to alternative splicing. The poly(A) tail is important for the nuclea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messenger RNA
In 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. These are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. This exon sequence constitutes mature mRNA. Mature mRNA is then read by the ribosome, and the ribosome creates the protein utilizing amino acids carried by transfer RNA (tRNA). This process is known as translation. All of these processes form part of the central dogma of molecular biology, which describes the flow of genetic information in a biological system. As in DNA, genetic inf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNase D
RNase D is one of the seven exoribonuclease An exoribonuclease is an exonuclease ribonuclease, which are enzymes that degrade RNA by removing terminal nucleotides from either the 5' end or the 3' end of the RNA molecule. Enzymes that remove nucleotides from the 5' end are called ''5'-3 ...s identified in '' E. coli''. It is a 3'-5' exoribonuclease which has been shown to be involved in the 3' processing of various stable RNA molecules. RNase D has homologues in many other organisms like eubacteria and eukaryotes, and has been shown to contribute to the 3' maturation of several stable RNAs. When a part of another larger protein has a domain that is very similar to RNase D, this is called an RNase D domain. References External links Crystal structure of ''E. coli'' RNase D at the RCSB Protein Data Bank Ribonucleases EC 3.1.13 {{3.1-enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exonuclease
Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. Its close relative is the endonuclease, which cleaves phosphodiester bonds in the middle (endo) of a polynucleotide chain. Eukaryotes and prokaryotes have three types of exonucleases involved in the normal turnover of mRNA: 5′ to 3′ exonuclease (Xrn1), which is a dependent decapping protein; 3′ to 5′ exonuclease, an independent protein; and poly(A)-specific 3′ to 5′ exonuclease. In both archaea and eukaryotes, one of the main routes of RNA degradation is performed by the multi-protein exosome complex, which consists largely of 3′ to 5′ exoribonucleases. Significance to polymerase RNA polymerase II is known to be in effect during transcriptional termination; it works with a 5' exonuclease (human gene Xrn2) to degrade the newly formed transcr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dyskeratosis Congenita
Dyskeratosis congenita (DKC), also known as Zinsser-Engman-Cole syndrome, is a rare progressive congenital disorder with a highly variable phenotype. The entity was classically defined by the triad of abnormal skin pigmentation, nail dystrophy, and leukoplakia of the oral mucosa, and myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML), but these components do not always occur. DKC is characterized by short telomeres. The disease initially can affect the skin, but a major consequence is progressive bone marrow failure which occurs in over 80%, causing early mortality. Presentation DKC can be characterized by cutaneous pigmentation, premature graying, dystrophy of the nails, leukoplakia of the oral mucosa, continuous lacrimation due to atresia of the lacrimal ducts, often thrombocytopenia, anemia, testicular atrophy in the male carriers, and predisposition to cancer. Also, liver abnormalities are associated with this syndrome, Nodular Regenerative Hypoplasia of the liv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
