משתמש:בנצי/ארגז חול ג': תיבת TATA
The TATA box (also called Goldberg-Hogness box)[1] is a DNA sequence (cis-regulatory element) found in the promoter region of genes in archaea and eukaryotes;[2] approximately 24% of human genes contain a TATA box within the core promoter.[3]
Considered to be the core promoter sequence, it is the binding site of either general transcription factors or histones (the binding of a transcription factor blocks the binding of a histone and vice versa) and is involved in the process of transcription by RNA polymerase.
Overview[עריכת קוד מקור | עריכה]
The TATA box has the core DNA sequence 5'-TATAAA-3' or a variant, which is usually followed by three or more adenine bases [דרוש מקור]. It is usually located 25 base pairs upstream of the transcription site. The sequence is believed to have remained consistent throughout much of the evolutionary process, possibly originating in an ancient eukaryotic organism.
It is normally bound by the TATA binding protein (TBP) in the process of transcription, which unwinds the DNA, and bends it through 80°. The AT-rich sequence facilitates easy unwinding (due to weaker base-stacking interactions among A and T than G and C). The TBP is an unusual protein in that it binds to the minor groove and binds with a β sheet.
The TATA box is usually found at the binding site of RNA polymerase II. TFIID, a transcription factor, binds to the TATA box, followed by TFIIA binding to the upstream part of TFIID. TFIIB can then bind to the downstream part of TFIID. The polymerase can then recognize this multi-protein complex and bind to it, along with various other transcription factors such as TFIIF, TFIIE and TFIIH. Transcription is then initiated, and the polymerase moves along the DNA strand, leaving TFIID and TFIIA bound to the TATA box. These can then facilitate the binding of additional RNA polymerase II molecules.
This cluster of RNA polymerase II and various transcription factors is known as a basal transcriptional complex (BTC). In this state, it only gives a low level of transcription. Other factors must stimulate the BTC to increase transcription levels. One such example of a BTC stimulating region of DNA is the CAAT box.
Most genes lack a TATA box and use an initiator element or downstream core promoter (DCE) instead.[דרוש מקור] Nevertheless, TBP is always involved and is forced to bind without sequence specificity. A genome-wide study put the fraction of TATA-dependent human promoters at ~10%.[4] An earlier study of ~1,000 genes found 32% of the promoters had a TATA box.[5]
See also[עריכת קוד מקור | עריכה]
הערות שוליים[עריכת קוד מקור | עריכה]
- ^ Lifton RP, Goldberg ML, Karp RW, Hogness DS (1978). "The organization of the histone genes in Drosophila melanogaster: functional and evolutionary implications". Cold Spring Harb Symp Quant Biol. 42: 1047–1051. PMID 98262.
{{cite journal}}: תחזוקה - ציטוט: multiple names: authors list (link) - ^ Smale, ST; Kadonaga, JT (2003). "The RNA polymerase II core promoter" (PDF). Annual review of biochemistry. 72: 449–79. doi:10.1146/annurev.biochem.72.121801.161520. PMID 12651739.
- ^ Yang, C; Bolotin, E; Jiang, T; Sladek, FM; Martinez, E (2007). "Prevalence of the initiator over the TATA box in human and yeast genes and identification of DNA motifs enriched in human TATA-less core promoters". Gene. 389 (1): 52–65. doi:10.1016/j.gene.2006.09.029. PMC 1955227. PMID 17123746.
- ^ Carninci P, Sandelin A, Lenhard B; et al. (ביוני 2006). "Genome-wide analysis of mammalian promoter architecture and evolution". Nat. Genet. 38 (6): 626–35. doi:10.1038/ng1789. PMID 16645617.
{{cite journal}}: (עזרה); Explicit use of et al. in:|author=(עזרה)תחזוקה - ציטוט: multiple names: authors list (link) - ^ Suzuki Y, Tsunoda T, Sese J; et al. (במאי 2001). "Identification and characterization of the potential promoter regions of 1031 kinds of human genes". Genome Res. 11 (5): 677–84. doi:10.1101/gr.164001. PMC 311086. PMID 11337467.
{{cite journal}}: (עזרה); Explicit use of et al. in:|author=(עזרה)תחזוקה - ציטוט: multiple names: authors list (link)