HIV Genome Pdf

Presentation Notes of HIV AIDS Genome Size, Structure & Organization in word/ .ppt for Medical & Biology Students 

HIV GENOME


HIV has just nine genes (compared to more than 500 genes in a bacterium, and around 20,000-25,000 in a human). Three of the HIV genes, called gag, pol and env, contain information needed to make structural proteins for new virus particles. The other six genes, known as tat, rev, nef, vif, vpr and vpu, code for proteins that control the ability of HIV to infect a cell, produce new copies of virus, or cause disease.

 
Diagram of the HIV Genome 

HIV has several major genes coding for structural proteins that are found in all retroviruses, and several nonstructural ("accessory") genes that are unique to HIV. The gag gene provides the basic physical infrastructure of the virus, and pol provides the basic mechanism by which retroviruses reproduce, while the others help HIV to enter the host cell and enhance its reproduction. Though they may be altered by mutation, all of these genes except tev exist in all known variants of HIV.

  • gag (Group-specific Antigen): codes for p24, the viral capsid; p6 and p7, the nucleocapsid proteins; and p17, a matrix protein. 
  • pol: Codes for viral enzymes, the most important of which are reverse transcriptase, integrase, and protease which cleaves the proteins derived from gag and pol into functional proteins. 
  • env (for "envelope"): Codes for the precursor to gp120 and gp41, proteins embedded in the viral envelope which enable the virus to attach to and fuse with target cells. 
  • Tat ( trans activating gene) enhancing the expression of all viral genes. 
  • Nef (negative factor gene) down regulating viral replication. 
  • Rev ( regulator of virus gene) enhancing expression of structural proteins. 
  • Vif ( viral infectivity factor gene) influencing infectivity of viral particles. 
  • Vpu (in HIV-1) and vpx (in HIV-2) believed to enhance maturation and release of progeny virus from cells (Detection of the type-specific sequences vpu and vpx is useful in distinguishing between infection by HIV 1 and 2). 
  • Vpr reported to stimulate the promoter region of the virus. 
  • LTR (long terminal repeat) sequences, one at either end, containing sequences giving promoter, enhancer and integration signals. 
  • tev: This gene is only present in a few HIV-1 isolates. It is a fusion of parts of the tat, env, and rev genes, and codes for a protein with some of the properties of Tat, but little or none of the properties of Rev. 

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