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Cap Snatching
The first step of transcription for some negative, single-stranded RNA viruses is cap snatching, in which the first 10 to 20 residues of a host cell RNA are removed (snatched) and used as the 5′ cap and primer to initiate the synthesis of the nascent viral mRNA. The viral RNA-dependent RNA polymerase (RdRp) can then proceed to replicate the negative-sense genome from the positive-sense template. Cap-snatching also explains why some viral mRNA have 5’ terminal extensions of 10-20 nucleotides that are not encoded for in the genome. Examples of viruses that engage in cap-snatching include influenza viruses ('' Orthomyxoviridae''), Lassa virus ('' Arenaviridae''), hantaan virus (''Hantaviridae'') and rift valley fever virus (''Phenuiviridae''). Most viruses snatch 15-20 nucleotides except for the families ''Arenaviridae'' and ''Nairoviridae'' and the genus Thogotovirus (''Orthomyxoviridae'') which use a shorter strand. In the influenza virus, cap snatching occurs in the nucleus o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baloxavir Marboxil
Baloxavir marboxil, sold under the brand name Xofluza, is an antiviral medication for treatment of influenza A and influenza B flu. It was approved for medical use both in Japan and in the United States in 2018, and is taken as a single dose by mouth. It may reduce the duration of flu symptoms by about a day, but is prone to selection of resistant mutants that render it ineffectual. Baloxavir marboxil was developed as a prodrug strategy, with its metabolism releasing the active agent, baloxavir acid (BXA). Baloxavir acid then functions as enzyme inhibitor, targeting the influenza virus' cap-dependent endonuclease activity, used in "cap snatching" by the virus' polymerase complex, a process essential to its life-cycle. The most common side effects of baloxavir marboxil include diarrhea, bronchitis, nausea, sinusitis, and headache. The US Food and Drug Administration (FDA) considers baloxavir marboxil to be a first-in-class medication. Medical uses Baloxavir marboxil is an inf ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the double-stranded DNA so that one strand of the exposed nucleotides can be used as a template for the synthesis of RNA, a process called transcription. A transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region before RNAP can initiate the DNA unwinding at that position. RNAP not only initiates RNA transcription, it also guides the nucleotides into position, facilitates attachment and elongation, has intrinsic proofreading and replacement capabilities, and termination recognition capability. In eukaryotes, RNAP can build chains as long as 2.4 million nucleotides. RNAP produces RNA that, functionally, is either for protein coding, i.e. messenger RNA (mRNA); or n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribonuclease
Ribonuclease (commonly abbreviated RNase) is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the EC 2.7 (for the phosphorolytic enzymes) and 3.1 (for the hydrolytic enzymes) classes of enzymes. Function All organisms studied contain many RNases of two different classes, showing that RNA degradation is a very ancient and important process. As well as clearing of cellular RNA that is no longer required, RNases play key roles in the maturation of all RNA molecules, both messenger RNAs that carry genetic material for making proteins and non-coding RNAs that function in varied cellular processes. In addition, active RNA degradation systems are the first defense against RNA viruses and provide the underlying machinery for more advanced cellular immune strategies such as RNAi. Some cells also secrete copious quantities of non-specific RN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Influenza Virus
''Orthomyxoviridae'' (from Greek ὀρθός, ''orthós'' 'straight' + μύξα, ''mýxa'' 'mucus') is a family of negative-sense RNA viruses. It includes seven genera: ''Alphainfluenzavirus'', ''Betainfluenzavirus'', '' Gammainfluenzavirus'', '' Deltainfluenzavirus'', ''Isavirus'', ''Thogotovirus'', and ''Quaranjavirus''. The first four genera contain viruses that cause influenza in birds (see also avian influenza) and mammals, including humans. Isaviruses infect salmon; the thogotoviruses are arboviruses, infecting vertebrates and invertebrates (such as ticks and mosquitoes). The Quaranjaviruses are also arboviruses, infecting vertebrates (birds) and invertebrates (arthropods). The four genera of Influenza virus that infect vertebrates, which are identified by antigenic differences in their nucleoprotein and matrix protein, are as follows: * ''Alphainfluenzavirus'' infects humans, other mammals, and birds, and causes all flu pandemics * ''Betainfluenzavirus'' infects humans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thogotovirus
''Thogotovirus'' is a genus of enveloped RNA viruses, one of seven genera in the virus family ''Orthomyxoviridae''. Their single-stranded, negative-sense RNA genome has six or seven segments. Thogotoviruses are distinguished from most other orthomyxoviruses by being arboviruses – viruses that are transmitted by arthropods, in this case usually ticks. Thogotoviruses can replicate in both tick cells and vertebrate cells; one subtype has also been isolated from mosquitoes. A consequence of being transmitted by blood-sucking vectors is that the virus must spread systemically in the vertebrate host – unlike influenza viruses, which are transmitted by respiratory droplets and are usually confined to the respiratory system. The genus contains the species '' Thogoto thogotovirus'' and ''Dhori virus'' (DHOV), and the latter's subtype Batken virus, as well as the species or strains Araguari virus, Aransas Bay virus (ABV), Bourbon virus, Jos virus (JOSV) and Upolu virus (UPOV), whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenuiviridae
''Phenuiviridae'' is a family of negative-strand RNA viruses in the order ''Bunyavirales''. Ruminants, camels, humans, and mosquitoes serve as natural hosts. Member genus ''Phlebovirus'' is the only genus of the family that has viruses that cause disease in humans (e.g. Rift Valley fever virus) except Dabie bandavirus. Virology Structure Members of ''Phenuiviridae are'' enveloped viruses with helical capsid morphology. Envelope glycoproteins of these viruses are distributed with icosahedral symmetry (T=12). Genome ''Phenuiviridae'' is a negative-sense single-stranded RNA virus family. Its genome is segmented into three pieces: L segment (encoding RNA-dependent RNA polymerase), M segment, and S segment. Some members of the family have ambisense gene encoding on the S segment ( nucleocapsid proteins). The M segment includes envelope glycoproteins encoded in a polyprotein that is cleaved by host proteases. Multiple different proteins can be encoded on the M segment due ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hantaviridae
''Hantaviridae'' is a family of viruses in the order ''Bunyavirales''. It is named for the Hantan River area in South Korea where an early outbreak of one of its species was observed. Taxonomy * '' Actantavirinae'' ** '' Actinovirus'' * '' Agantavirinae'' ** '' Agnathovirus'' * '' Mammantavirinae'' ** '' Loanvirus'' ** '' Mobatvirus'' ** ''Orthohantavirus ''Orthohantavirus'' is a genus of single-stranded, enveloped, negative-sense RNA viruses in the family '' Hantaviridae'' within the order ''Bunyavirales''. Members of this genus may be called orthohantaviruses or simply hantaviruses. Orthohantav ...'' ** '' Thottimvirus'' * '' Repantavirinae'' ** '' Reptillovirus'' References {{Taxonbar, from=Q29001075 Virus families Bunyavirales ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transcription Initiation
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. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter DNA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hantaan Virus
''Hantaan orthohantavirus'' (HTNV) is an enveloped, single-stranded, negative-sense RNA virus species of Old World ''Orthohantavirus''. It is the causative agent of Korean hemorrhagic fever in humans. It is named for the Hantan River in South Korea, and in turn lends the name to its genus ''Orthohantavirus'' and family ''Hantaviridae''. Natural reservoir '' Apodemus agrarius'', also known as striped field mouse, is the etiological vector of ''Hantaan orthohantavirus''. Transmission Transmission is believed to be through inhalation of aerosolized rodent urine and feces. Morbidity and mortality In hantavirus induced hemorrhagic fever, incubation time is between two and four weeks in humans before symptoms of infection present. Severity of symptoms depends on the viral load. Like Dobrava-Belgrade virus, Hantaan virus has a mortality rate of 10 to 12%. History During the Korean War (1951–1953), more than 3000 American and Korean troops fell ill with kidney failure, ble ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
