The human immunodeficiency virus, or HIV, causes AIDS, a disease for which there is no cure. The virus is sexually transmitted, but is also spread during pregnancy, breastfeeding or having contact with infected blood. HIV attacks the immune system, and it uses the Tat protein to do so, as well as to duplicate itself.
HIV
HIV is a retrovirus; that is, the virus has an enzyme called reverse transcriptase that changes its RNA genetic material into DNA. Enzymes are proteins used to make a reaction go at a faster rate. In human cells, DNA is used to make RNA, but the human immunodeficiency virus does not have DNA, so it goes in reverse. Once it makes DNA, the DNA enters the chromosomes of the infected cells, signaling them to make more viruses.
HIV Structure
HIV is approximately 100 nm in diameter. The outermost structure of the virus is called the membrane envelope. Underneath the membrane envelope is the matrix protein, and inside the matrix protein are two molecules of RNA, which are surrounded by an outer shell referred to as a capsid. There are proteins embedded in the membrane envelope, and the virus has three enzymes inside the capsid that contains the RNA molecules whose only purpose is to help the virus duplicate itself. It also has several genes and proteins, including the tat gene and Tat protein.
The Tat Protein
The tat gene leads to the production of the Tat protein. This is a protein that the virus must have, along with the three enzymes, to duplicate. In addition, the Tat protein makes human cells release proteins called cytokines. Cytokines help regulate the response of the immune system. According to an article in the December 2008 issue of the "European Journal of Cell Biology," having an increased number of cytokines in an HIV infection may be how the virus lowers the response of the human immune system, making it defective and unable to attack HIV.
Research Study on Tat Protein
An article in the June 2008 issue of "BMC Cell Biology," explains how the Tat protein is primarily in the nucleolus of an infected human cell. A nucleolus is the name of the structure inside the nucleus where ribosomes are made; proteins are made in the ribosomes. The article details a study that was done to determine why the Tat protein is in the nucleolus. Using the Drosophila fly, the scientists found that the Tat protein interferes with the creation of ribosomes and causes a decrease of ribosomes in the cytoplasm of a cell.
References
- "BMC Cell Biology"; HIV Tat protein affects processing of rRNA; Donatella Ponti et al.; Dec. 2008
- "European Journal of Cell Biology"; HIV-1 Tat protein induces IL-10; Kaoutar Leghmaria et al.; June 2008
- "Sherris Medical Microbiology"; Kenneth Ryan, M.D., C. George Ray, M.D.; 2010
