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Early Protein
The classification of viral proteins as early proteins or late proteins depends on their relationship with genome replication. While many viruses (such as HIV) are described as expressing early and late proteins, this definition of these terms is commonly reserved for class I DNA viruses. (HIV has two stages of protein expression but these are not as a result of two stages of transcription surrounding replication but by the production of the Rev protein which is required for the export of the transcripts of the second set of proteins transcribed form the cell nucleus.) Early proteins are those produced following entry into the host cell but prior to replication. The expression of early genes, commonly encoding non-structural proteins, initiates replication of the genome and expression of late genes. In some, simpler viruses, this pattern of expression is clearly defined, while in those with more complex genomes, such as the herpesviruses, these expression periods overlap. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proteins
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, providing structure to cells and organisms, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific 3D structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide. Short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residues ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Proteins
A late protein is a viral protein that is formed after replication of the virus. One example is VP4 from simian virus 40 (SV40). In Human papillomaviruses In Human papillomavirus (HPV), two late proteins are involved in capsid formation: a major (L1) and a minor (L2) protein, in the approximate proportion 95:5%. L1 forms a pentameric assembly unit of the viral shell in a manner that closely resembles VP1 from polyomaviruses. Intermolecular disulphide bonding holds the L1 capsid proteins together. L1 capsid proteins can bind via its nuclear localisation signal (NLS) to karyopherins Kapbeta(2) and Kapbeta(3) and inhibit the Kapbeta(2) and Kapbeta(3) nuclear import pathways during the productive phase of the viral life cycle. Surface loops on L1 pentamers contain sites of sequence variation between HPV types. L2 minor capsid proteins enter the nucleus twice during infection: in the initial phase after virion disassembly, and in the productive phase when it assembles into replicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as regulatory sequences (see non-coding DNA), and often a substantial fraction of 'junk' DNA with no evident function. Almost all eukaryotes have mitochondria and a small mitochondrial genome. Algae and plants also contain chloroplasts with a chloroplast genome. The study of the genome is called genomics. The genomes of many organisms have been sequenced and various regions have been annotated. The International Human Genome Project reported the sequence of the genome for ''Homo sapiens'' in 200The Human Genome Project although the initial "finished" sequence was missing 8% of the genome consisting mostly of repetitive sequences. With advancements in technology that could handle sequenci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Replication
Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them. Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm. Viral production / replication Viruses multiply only in living cells. The host cell must provide the energy and synthetic machinery and the low- molecular-weight precursors for the synthesis of viral proteins and nucleic acids. The virus replication occurs in seven stages, namely; # Attachment # Entry, # Uncoating, # Transcription / mRNA production, # Synthesis of virus components, # Virion assembly and # Release (Liberation Stage). Attachment It is the first step of viral replication ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Protein
A late protein is a viral protein that is formed after replication of the virus. One example is VP4 from simian virus 40 (SV40). In Human papillomaviruses In Human papillomavirus (HPV), two late proteins are involved in capsid formation: a major (L1) and a minor (L2) protein, in the approximate proportion 95:5%. L1 forms a pentameric assembly unit of the viral shell in a manner that closely resembles VP1 from polyomaviruses. Intermolecular disulphide bonding holds the L1 capsid proteins together. L1 capsid proteins can bind via its nuclear localisation signal (NLS) to karyopherins Kapbeta(2) and Kapbeta(3) and inhibit the Kapbeta(2) and Kapbeta(3) nuclear import pathways during the productive phase of the viral life cycle. Surface loops on L1 pentamers contain sites of sequence variation between HPV types. L2 minor capsid proteins enter the nucleus twice during infection: in the initial phase after virion disassembly, and in the productive phase when it assembles into replicat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Virus
A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and those that have one strand of DNA in their genome, called single-stranded DNA (ssDNA) viruses. dsDNA viruses primarily belong to two realms: ''Duplodnaviria'' and ''Varidnaviria'', and ssDNA viruses are almost exclusively assigned to the realm ''Monodnaviria'', which also includes some dsDNA viruses. Additionally, many DNA viruses are unassigned to higher taxa. Reverse transcribing viruses, which have a DNA genome that is replicated through an RNA intermediate by a reverse transcriptase, are classified into the kingdom '' Pararnavirae'' in the realm '' Riboviria''. DNA viruses are ubiquitous worldwide, especially in marine environments where they form an important part of marine ecosystems, and infect both prokaryotes and eukaryotes. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. These products are often proteins, but in non-protein-coding genes such as transfer RNA (tRNA) and small nuclear RNA (snRNA), the product is a functional non-coding RNA. Gene expression is summarized in the central dogma of molecular biology first formulated by Francis Crick in 1958, further developed in his 1970 article, and expanded by the subsequent discoveries of reverse transcription and RNA replication. The process of gene expression is used by all known life—eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea), and utilized by viruses—to generate the macromolecular machinery for life. In genetics, gene expression is the most fundamental level at which the genotype gives rise to the phenotype, '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rev (HIV)
Rev is a transactivating protein that is essential to the regulation of HIV-1 (and other lentiviral) protein expression. A nuclear localization signal is encoded in the ''rev'' gene, which allows the Rev protein to be localized to the nucleus, where it is involved in the export of unspliced and incompletely spliced mRNAs. In the absence of Rev, mRNAs of the HIV-1 late (structural) genes are retained in the nucleus, preventing their translation. History A novel protein was found to be involved in the translation of ''gag'' and ''env'' mRNA. The unknown protein functioned by removing repression of regulatory sequences and was named Art (anti-repression transactivator). Later studies suggested that the protein was involved in regulation of the RNA splicing mechanism. Therefore, the name of the protein was modified from Art to Trs (transregulator of splicing). The most recent studies have shown that the protein has multiple functions in the regulation of HIV-1 proteins, and its name h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Nucleus
The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') 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. The cell nucleus contains nearly all of the cell's genome. Nuclear DNA is often organized into multiple chromosomes – long stands of DNA dotted with various proteins, such as histones, that protect and organize the DNA. The genes within these chromosomes are structured in such a way to promote cell function. The nucleus maintains the integrity of genes and controls the activities of the cell by regulating gene expres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Entry
Viral entry is the earliest stage of infection in the viral life cycle, as the virus comes into contact with the host cell (biology), cell and introduces viral material into the cell. The major steps involved in viral entry are shown below. Despite the variation among viruses, there are several shared generalities concerning viral entry. Reducing cellular proximity How a virus enters a cell is different depending on the type of virus it is. A virus with a Viral envelope, nonenveloped capsid enters the cell by attaching to the attachment factor located on a host cell. It then enters the cell by endocytosis or by making a hole in the membrane of the host cell and inserting its viral genome. Cell entry by enveloped viruses is more complicated. Enveloped viruses enter the cell by attaching to an attachment factor located on the surface of the host cell. They then enter by endocytosis or a direct membrane fusion event. The fusion event is when the virus membrane and the host cell m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viral Replication
Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome and packaging these copies, the virus continues infecting new hosts. Replication between viruses is greatly varied and depends on the type of genes involved in them. Most DNA viruses assemble in the nucleus while most RNA viruses develop solely in cytoplasm. Viral production / replication Viruses multiply only in living cells. The host cell must provide the energy and synthetic machinery and the low- molecular-weight precursors for the synthesis of viral proteins and nucleic acids. The virus replication occurs in seven stages, namely; # Attachment # Entry, # Uncoating, # Transcription / mRNA production, # Synthesis of virus components, # Virion assembly and # Release (Liberation Stage). Attachment It is the first step of viral replication ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herpesvirus
''Herpesviridae'' is a large family of DNA viruses that cause infections and certain diseases in animals, including humans. The members of this family are also known as herpesviruses. The family name is derived from the Greek word ''ἕρπειν'' ( 'to creep'), referring to spreading cutaneous lesions, usually involving blisters, seen in flares of herpes simplex 1, herpes simplex 2 and herpes zoster (shingles). In 1971, the International Committee on the Taxonomy of Viruses (ICTV) established ''Herpesvirus'' as a genus with 23 viruses among four groups. As of 2020, 115 species are recognized, all but one of which are in one of the three subfamilies. Herpesviruses can cause both latent and lytic infections. Nine herpesvirus types are known to primarily infect humans, at least five of which – herpes simplex viruses 1 and 2 (HSV-1 and HSV-2, also known as HHV-1 and HHV-2; both of which can cause orolabial herpes and genital herpes), varicella zoster virus (or HHV-3; the cause o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
