TRAP
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Tandem Repeats
Definition
Definition
TAAT is a DNA consensus sequence that is bound by regulatory proteins, for instance ! homeobox genes.
Tandem repeats are multiple copies of the same sequence lying in series.
TAG12 Definition Tumor-associated antigen 12 (TAG12); ! micrometastasis.
TAL-1 Definition T-cell acute lymphocytic leukemia 1 (Tal-1), also known as Scl1 or Tcl-5, is a bHLH protein member of the Lyl family of 331 amino acids and 34 kD. The human TAL1, SCL or TCL5 gene locus maps to 1p32 and the mouse tal1 gene locus at chromosome 4 (49.50 cM). Tal1 is implicated in the genesis of hemopoietic malignancies. A form of stem cell leukemia is characterized by a chromosomal translocation t(1;14)(p32;q11) that involves Tal1 and T-cell receptor a chain genes. Tal-1 may play an important role in hemopoietic differentiation, serving as a positive regulator of erythroid differentiation.
Target Validation Definition Target validation is the demonstration that a protein is involved in or required for a disease-relevant cellular process. Target validation is an early rate limiting step in drug discovery and hence is very important in developing new therapies.
TAT Protein of HIV Adriana Albini, Douglas Noonan National Cancer Research Institute ± Genova, Genova, Italy [email protected]; [email protected]
Definition Tat is a small viral protein that is encoded by the spliced two-exon tat gene in the HIV genome, responsible for transactivation of the HIV genome.
Characteristics The HIV Tat protein gets its name from its principal activity, Tat stands for Transactivator,
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TAT Protein of HIV
which means that it binds to DNA and activates the transcription of DNA into RNA. The Tat protein has an important role in controlling the transcription of the lentivirus HIV genome from its built-in `promoter', known as the long terminal repeat (which refers to its structure) or LTR, to make the RNA that forms new HIV virus particles. In addition to this major role, Tat has also been implicated in a wide variety of pathologies encountered in persons infected with HIV. How does this small (about 101 amino acids) Tat protein do this? Tat has a capacity to bind a striking number of different proteins, nucleic acids and even polysaccharides. It is this combination of binding to different partners that has linked Tat to numerous events in AIDS and intrigued many researchers, making Tat one of the most extensively studied HIV proteins. Transcriptional regulation: control of HIV replication The HIV ! LTR acts as a gene promoter. The gene promoter is a portion of DNA that mediates the binding of RNA polymerase (usually through a series of other proteins that bind to the promoter DNA as well) at the beginning of the gene to be transcribed into RNA. This interaction of proteins with DNA controls the transcription of each gene so that it occurs at a certain moment. In the absence of Tat, very little RNA is transcribed from the HIV LTR promoter. When Tat is present, the rate of transcription shoots up several hundred fold,
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