HIV molecular biology. BTY328: Virology [email protected] Retroviruses. Oncoviruses : cancer causing eg. HTLV Lentiviruses : slow virus diseases eg. HIV-1 and HIV-2 Spumaviruse s: not associated with human disease.
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HIV surface membrane has glycoproteins gp41 and gp120
gp120 binds to CD4 receptor on CD4+ cell (T lymphocytes)
gp41 binds to a cytokine receptor, either CCR5 or CXCR4, fusing viral envelope with cell membrane and releases the capsid into the cell.
Nucleocapsid contains two single stranded RNA molecules, as well as reverse transcriptase, which makes dsDNA from the RNA.
dsDNA is transported to nucleus by viral protein R (VPR)
HIV integrase iserts viral dsDNA into host cell
Incorporated viral DNA is transcribed onto two mRNAs,
one strand contains information for HIV structural proteins
other serves as genetic material of new virus
Translated polypeptide is cleaved by protease, making functional HIV proteins
HIV Structural proteins spontaneously assemble
around RNA and viral proteins, forming new virus
Virus is encapsulated by cell membrane and buds off (exocytosis)
Through mechanisms not understood (adoptosis) host cells die.
Integrase catalyzes two reactions;
GAG- group specific antigens make up viral nucleocapsid- cylindrical core proteins (p24: a nucleoid shell protein with mol. wt. 24,000) and several internal proteins.When GAG is non-functional HIV loses ability to bud out of cell.
POL codes for the following HIV enzymes: P10 protease, reverse transcriptase, endonuclease /integrase
ENV codes for two major HIV surface proteins- gp120: located on external spikes of HIV and gp 41: transmembrane protein that attaches gp120 to surface of HIV.
Regulator of Expression of Viral proteins
Nef: N-myristylated and anchored to inner surface of plasma membrane, probably in a complex with a cellular serine kinase.
Makes cell more capable of producing HIV progeny