HIV-infected T cell FLICKR, NIAID HIV leads to AIDS primarily because the virus destroys essential immune cells called CD4 T cells, but precisely how these cells are killed has not been clear. Two papers published simultaneously today (December 19) in Nature and Science reveal the molecular mechanisms that cause the death of most CD4 T cells in lymphoid tissues, the main reservoir for such cells, during infection.
Transcription is carried out by an enzyme called RNA polymerase and a number of accessory proteins called transcription factors. Transcription factors can bind to specific DNA sequences called enhancer and promoter sequences in order to recruit RNA polymerase to an appropriate transcription site. Together, the transcription factors and RNA polymerase form a complex called the transcription initiation complex.
In DNA, regulation of gene expression normally happens at the level of RNA biosynthesis (transcription), and is accomplished through the sequence-specific binding of proteins (transcription factors) that activate or inhibit transcription.Transcription factors may act as activators, repressors, or both.n DNA, regulation of gene expression normally happens at the level of RNA biosynthesis (transcription), and is accomplished through the sequence-specific binding of proteins (transcription factors) that activate or inhibit transcription. Transcription factors may act as activators, repressors, or both.