The genome of RNA is translated to produce a polyprotein which is able to be categorized into three diverse sections such as P1, P2, and P3. The RNA genome includes two kinds of proteins (structural and nonstructural) which are created by proteases effect. P1 region consists of the structural capsid proteins such as 1A (VP4), 1B (VP2), 1C (VP3), and 1D (VP1). However, P2 and P3 sections comprise of the non-structural replication proteins 2A, 2B, 2C, 3A, 3B (VPg), 3C, and 3D and also cleave the intermediates (2BC, 3AB, and 3CD) (Ryan, and Flint, 1997).
"Protein is a small hydrophobic membrane protein that localized at Endoplasmic Reticulum (ER) and Golgi membranes (4, 15, 33). Increasing evidence indicates that 2B forms homomultimers that build the pores in Endoplasmic Reticulum and Golgi complexmembranes" (1, 11, 12-14, 41). Furthermore, The expression of 2B can decrease the level of protein activitiy in the Golgi complex (14, 17). Consequently, the reduction of 2B protein cause restriction of viral RNA replication (9, 40). Pro 2
Pro 5: The proteolytic activity has a crucial effect on the function and structure of the host cells. For example, the maturation of mammalian digestive proteases and viral capsid protein production ()
Intro: "Picormaviruses are the smallest amd most economical animal pathogens" (ref 5 shomareye 5). The non-developed capsid, approximately 300° A in diameter, comprises 60 copies of 1A (VP4), 1B (VP2), 1C (VP3), and 1D (VP1) proteins and arranged in icosahedral pseudo TD3 symmetry (2).
The viral proteases of picornaviridae family cause cleavage the protein of the host cell and effect on it's metabolism some genera have 2A protease (such as Enterovirus, Rhinoviruses) and the others include L protein (e.g. Aphthoviruses). "2A protein enters the nucleus and associates with nucleoli, functionally altering newly formed ribosomes and causing them to preferentially translate IRES driven messages (44).
3C protein is able to cut the transcription factors between Gln-Gly pairs (46) to produce viral RNA molecules in the cell. However, the life cycle of picornaviruses occurs in cytoplasm, and 3C proteases do not have nuclear localization signal. So, it needs another factor (e.g. Poliovirus 3D protein) which helps it to reach the nucleus to finish it's function (47).
Virion structure of a Picornaviridae :Picornavirus virions consist of a non-enveloped, icosahedrally symmetric capsid. The capsid consists of 12 capsomers and has a diameter of 27-30 nm, which makes it one of the smallest of all viruses (thus the name "picornavirus"). The genome is tightly packed into the capsid. The capsid has four uniqueproteins:VP1,2,3,and4.Barayeshekel1 http://www.stanford.edu/group/virus/picorna/2004flynn/Picornaviridae2.htm
Replication of picornaviridae:Using different cellular receptors (depending on the picornavirus), a picornavirus virion attaches to a host cell. Uncoating occurs, and the virus' RNA is released into the cytoplasm of the host cell through a membrane channel. Virus replication occurs entirely in the cytoplasm. The host cell's transcription processes are shut off to a degree that varies with different picornaviruses, while the IRES helps to make sure the virus' transcription is left untouched. Replication occurs. RNA is packaged into preformed capsids. Release of the virus occurs when cell lysis occurs (with the exception of Hepatits A, which is non-lytic and thus creates a more persistent infection). Shekel 2 http://www.microbiologybytes.com/virology/Picornaviruses.html
Pic 3: In the picornavirus RNA there is a region of secondary structure called an internal ribosome entry site (IRES)
Pic 4: The proteases that cut up the original polyprotein are encoded in the virus genome and the proteolytic process is ordered
Pic 5: Attachment to the cell surface and entry of RNA into the cell pathmicro.med.sc.edu/virol/polio.htm
Pic 6: The surface of poliovirus indicating the canyon www.post-polionetwork.org.au/smforum/index.ph...
Pic 7: Rhinovirus 14 complexed with the ICAM-1 receptor, as solved by cryo-electron microscopy and image reconstruction. www.mirrorservice.org/.../BVRNApicorna.html
Pic 8: The polio virus receptor (CD155) interacting with the pocket in the virus. The viral proteins are VP1, VP2, VP3 and VP4. pathmicro.med.sc.edu/virol/polio.htm
Pic 9: Rhinovirus 14 bound to its receptor pathmicro.med.sc.edu/virol/polio.htm
Pic 10,11: A. The picornavirus binds to a receptor on the cell surface (A). RNA with VPg at the 5' end is translated into one primary translation product (B) which is then cleaved (C). The positive strand genomic RNA also associates with an RNA polymerase that is bound to the cytoplasmic surface of vesicles, probably from the endoplasmic reticulum, and is copied to negative stand RNA. VPg is also at the 5' end of the negative strand (the poly U end) (D). The negative strand is copied to genomic positive strand RNA (E) which associates with the procapsid to form a 150S virus (G) that is released on cell lysis B. Replication of a positive strand RNA virus pathmicro.med.sc.edu/virol/polio.htm
Pic 12: When the cell is infected by a picornavirus, the endoplasmic reticulum to Golgi body transport vesicles do not fuse with the cis face of the Golgi body pathmicro.med.sc.edu/virol/polio.htm
"FMDV was one of the first viruses to be recognized poliomyetilis as a viral disease was first recognized by Landsteiner and Popper, 1999" (picorna 1).
Both 3C and 3CD include RNA-binding and protease activities. However, RNA-binding activity is only needed for VPg function (3,4).
Picornaviruses are life threatening and the source of human and veterinary diseases such as poliomyelitis, the common cold, summer flu, hepatitis amd foot amd mouth disease (1).
A VPg which is a virion protein genome-linked binds to the 5′ ens of the plus strand genome and a poly A tail links to 3′ end (1).
Safheye 5: Most of the molecules which inhibit the picornaviruses replication are divided into two groups. The former is structural VP1,3C, and 2A protease and the latter is non structural proteins such as 3A and 2C.
Rueckert, and Wimmer,
