O

(CH) N-linked carbohydrate chains H Helical regions of PrPc X GPI (glycosyl phosphatidylinositol) 0 P-sheets in PrPc FIGURE 7.15 Isoforms of the human prion protein. The precursor protein is 254 amino acids long. Maturation involves removal of the N-terminal signal sequence and the C-terminal 23 amino acids (two boxes marked S), attachment of the new C terminus to a GPI anchor, and N-linked glycosylation at Asn181 and Asn197. After exposure to scrapie prions, the protein is converted to PrPSc,...

Atomic Structure of Viruses Having Pseudo73 Symmetry

The structures of several picornaviruses and of a plant comovirus (cowpea mosaic virus) have also been solved to atomic resolution. The structures of these viruses are similar to those of the plant T 3 viruses, but the 180 subunits that form the virion are not all identical. A comparison of the structure of a T 3 virus with those of poliovirus and of cowpea mosaic virus is shown in Fig. 2.7. Poliovirus has 60 copies of each of three different proteins, whereas the comovirus has 60 copies of an...

Cfv Hsrv

Avian myeloblastosis (AMV) Avian myelocytomatosis (AMCV-29) Moloney sarcoma (MoMSV) Harvey murine sarcoma (HaMSV) Gardner-Arnstein Vertical including mothers' milk sexual transmission, blood Neonatal infection, sexual transmission, blood Mammary carcinoma, Worldwide T-cell lymphoma B-cell lymphoma T-cell lymphoma, neurological disorders TSP, HAMC

Info

Finkel-Biskis-Jenkins murine sarcoma virus Source Adapted from Fields et al. (1996, p. 309). aIn these names, p is for protein, gp is for glycoprotein, pp is for phosphoprotein, and the numbers are the approximate apparent *This is a retrovirus with two oncogenes. cfps and fes are the same oncogene derived from the avian and feline genomes, respectively. draf and mil are the same oncogene derived from the murine and avian genomes, respectively. Three different ras genes have been found in...

Penetration

After the virus binds to a receptor, the next step toward successful infection is the introduction of the viral genome into the cytoplasm of the cell, In some cases, a subviral particle containing the viral nucleic acid is introduced into the cell, This particle may be the nucleocapsid of the virus or it may be an activated core particle, For other viruses, only the nucleic acid is introduced, The protein(s) that promotes entry may be the same as the protein(s) that binds to the receptor, or it...

Lytic Infection or Latent Infection

In a lytic infection, the virus replicates to high titer, host cell macromolecular synthesis is shut down, and the host cell dies. Bacterial cells are usually actively lysed by the elaboration of a specific lysis product during bacteriophage infection. Animal viruses, in contrast, usually cause cell death by inducing apoptosis or programmed cell death. Apoptosis is a suicide pathway in which the mitochrondria cease to function, the cell destroys its DNA, and the cell fragments into small...

Atomic Structure of T3 Viruses

Because the simple viruses are regular structures, they will often crystallize, and such crystals may be suitable for X-ray diffraction, Several viruses formed using icosa-hedral symmetry principles have now been solved to atomic resolution, Among T 3 viruses, the structures of FIGURE 2.5 Gallery of three-dimensional reconstructions of icosahedral viruses from cryoelectron micrographs. All virus structures are surface shaded and are viewed along a twofold axis of symmetry. All of the images are...

Family Flaviviridae

The Flaviviridae are so-called from the prototype virus of the genus Flavivirus, yellow fever virus, flavus being the Latin word for yellow. The Flaviviridae are divided into three genera, the genus Flavivirus, the genus Pestivirus, and the genus Hepacivirus. A partial listing of viruses in the three genera is given in Table 3.10. In the discussion below, the term flavivirus refers only to members of the genus Flavivirus, unless otherwise specified. The genome organizations of members of the...

Meaninng Of Tateropox

FIGURE 6.3 Model for the replication of orthopox DNA. Replication is initiated by nicking one strand at the red arrow near the left end of the DNA. This is followed by primer extension and loopback to form an internal primer. Extension then occurs through the hairpin at the right end of the molecule to form a concatemer. Concatemer resolution occurs by nicking at the blue arrows. Parental DNA is shown in blue, new strands in red. Redrawn from data in Moyer and Graves (1981) and Traktman (1990)....

The ICTV Classification of Viruses

The International Committee on Taxonomy of Viruses (ICTV), a committee organized by the Virology Division of the International Union of Microbiological Societies, is attempting to devise a uniform system for the classification and nomenclature of all viruses. Viruses are classified into species on the basis of a close, but not necessarily identical, relationship. The decision as to what constitutes a species is arbitrary because a species usually contains many different strains that may differ...

Receptors for Virus Entry

The infection cycle of an animal virus begins with its attachment to a receptor expressed on the surface of a susceptible cell, followed by penetration of the genome, either naked or complexed with protein, into the cytoplasm. Binding often occurs in several steps. For many viruses, the virion first binds to an accessory receptor that is present in high concentrations on the surface of the cell. These accessory receptors are usually bound with low affinity, and binding often has a large...

Aau Uau X Aaa Uuu Aua Ggg

T-RNA slips on message as mRNA shifts one position to the right FIGURE 1.15 Proposed mechanism of the -1 ribosomal frameshift that occurs in ALV. The slippery sequence is shown in green. The asterisk identifies the UAG codon that terminates the upstream Gag-Pro ORF. Frameshifting is thought to require a pseudoknot downstream of the slippery sequence illustrated in Fig. 1.16 . Adapted from Fields et al. 1996, p. 577 and Goff 1997, p. 156 . virus to fine-tune the processing events, and this...

Vlb

FIGURE 4.20 Ambisence coding strategy of the S RNA of a phlebovirus, family Bunyaviridae, The mRNA for the N protein is synthesized from the S genome segment using primers derived by cap-snatching similar to the mechanism for influenza mRNA priming in Fig, 4,13 from cytoplasmic host mRNAs, The mRNA for the NSs protein is formed in the same way, but with vcRNA as the template, Diagonally striped boxes are the self-complementary termini, The loops in the middle of the viral genomic and...

Family Paramyxoviridae

The family Paramyxoviridae has six genera. These genera are shown in Table 4.3, together with representative viruses in each genus. The relationships among the genera are illustrated in the tree shown in Fig. 4.5. Each genus represents a distinct lineage. Furthermore, Respirovirus, Morbillivirus, Megamyxovirus, and Rubulavirus are more closely related to one another than to Pneumovirus and Metapneumovirus, and the family is divided into two subfamilies, Paramyxovirinae and Pneumovirinae. Many...

U

This is the only example known of a metalloprotease in viruses. Flaviviruses have capped genomes whose translation is cap-dependent. In contrast, the hepacivirus and pestivirus genomes are not capped and have an IRES in the 5' nontrans-lated region. Members of Flaviviridae do not have a poly A tail at the 3' end of the RNA. A stable stem-loop structure present at the 3' end of the Flavivirus genome is illustrated in Fig. 3.20. This structure is required for replication of the genomic RNA...

Does The Yellow Fever Still Exist

Aedes Aegypti Species

FIGURE 3.24 Crystal structure ribbon diagram of the dimer of the E protein of tick-borne encephalitis virus. This is a top view, looking down onto the surface of the virion. Numbered sites are those in which mutations alter the virulence of the virus. From Rey et al. 1995 . organ, causes the major symptoms of disease and the symptoms from which the name of the virus derives, jaundice following destruction of liver cells. The virus also replicates in other organs, such as kidney and heart, and...

I

Host DNA polymerase iral-encoded factor FIGURE 1.6 General replication scheme for a DNA virus. After a DNA virus attaches to a cellular membrane receptor, the virus DNA enters the cell and is transported to the cell nucleus. There it is transcribed into mRNA by host RNA polymerase. Viral mRNAs are translated by host ribosomes in the cytoplasm, and newly synthesized viral proteins, both structural and nonstructural, are transported back to the nucleus. After the DNA genome is replicated in the...

Q

FIGURE 6.26 Prevalence of antibodies to BK and JC viruses in humans in the United States as a function of age. From Fields et al. 1996 , p. 2039 . FIGURE 6.26 Prevalence of antibodies to BK and JC viruses in humans in the United States as a function of age. From Fields et al. 1996 , p. 2039 . piratory disease or cystitis bladder infection in young children, but most infections with either BK or JC virus are not associated with illness. The viruses establish a latent infection that persists...

B

1' DI 1 interferes strongly with replication of standard virus ST 1 . 2' A new variant of standard virus ST 2 emerges that is resistant to interference by DI 1 and does not serve as a helper for DI 1. 3' Without helper assistance, DI 1 disappears, and ST 2 replicates vigorously. 4' New DIs of ST 2 DI 2 appear and begin to depress ST 2 replication. FIGURE 7.3 Stylized illustration of the influence of defective interfering particles on viral evolution. A Short-term generation of DI particles...

Megamyxovirus Nipah

The respiratory tract infections caused by HPIV-1 and HPIV-3 may be limited to the upper respiratory tract, causing colds, or may also involve the lower respiratory tract, causing bronchopneumonia, bronchiolitis, or bronchitis. These viruses are widespread around the world and are an important cause of lower respiratory tract disease in young children. Serological studies have shown that most children are infected by HPIV-3 by 2-4 years of age, and that the incidence of infection can be as high...

Sv40

FIGURE 6.19 Known interactions between the oncogenic proteins shaded with pink patterns of an adenovirus, a polyomavirus, and a papil-lomavirus and cellular proteins that are regulators of cell cycle progression. A Protein E1A of adenoviruses binds to the Rb family, promoting entry into S phase. The 19-kDa form of E1B also binds to p53, blocking apoptosis. B The large T antigen of the polyomavirus, SV40, interacts with the Rb family of proteins as well as with p53 see also Fig. 6.25 . C The...

Viroids And Virusoids

Viroids are small, circular RNA molecules that do not encode any protein and that are infectious as naked RNA molecules. Sequenced viroids range from 246 to 375 nt and possess extensive internal base pairing that results in the RNA being rod-like and about 15 nm long. A partial listing of viroids is given in Table 7.1. All known viroids infect plants. However, hepatitis 8, which infects humans, has many viroid-like properties and may be related to viroids. Many viroids are important...

Ciebov Rebov

Contact with blood or other body fluids Contact with blood or other body fluids Severe hemorrhagic disease Africa Severe hemorrhagic disease Africa disease in monkeys, attenuated in man kidneys were being processed for cell culture production for use in preparing poliovirus vaccine . Twenty-five laboratory workers were infected and six secondary cases resulted of these 31 infected people, 7 died. The monkeys in the shipment, which originated in Uganda, also died. Subsequent studies with the...