Picornaviruses 2

have a non-enveloped, icosahedral capsid that encloses a ssRNA that is positive sense

60 copies of four proteins: VP1-4

they arrange themselves in a wedge-shaped jelly-roll, composed of an eight-stranded Beta-barrel structure

they form the capsid shell

rhinoviruses: receptor-mediated endocytosis

others bind to a receptor. They lose VP4 and VP1 is extruded to the cell surface

virus-encoded protein that is covalently attached to the 5' end of genome RNA and a poly(A) tract of 30-100 nucleotides

poly(A) is already part of the genome

employ cap-dependent mechanisms

the eIF-4F complex, with eIF-4A,E, and G recruits a 40S ribosomal subunit to the capped 5' end of an mRNA

the 40S subunit scans the mRNA, searching for AUG. THen, the 60S joins to form the 80S. Protein synthesis begins

proteolytic cleavage of eIF-4G or by sequestration of the cap-binding protein eIF-4E.

they initiate protein synthesis via an IRES that lies within the 5' noncoding region

Their mRNA codes for a single protein. It is a polyprptein that gets cleaved into different fx. polyproteins by proteinases. It is cleaved into P1-3

subsequently cleaved into capsid proteins VP0, 1, and 3

VP0--> VP2 and VP4

• L: cleaves itself from the VP4 an cleaves eIF-4G
• 2A: cleaves at the P1/P2 junction; cleaves eIF-4G
• 3C