# Selective factor 1

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Selective_factor_1
> Markdown URL: https://mediated.wiki/source/Selective_factor_1.md
> Source: https://en.wikipedia.org/wiki/Selective_factor_1
> Source revision: 1321956021
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{Short description|Mammalian protein found in Homo sapiens}}
thumb|500px|Role of transcription factor in gene expression regulation
'''Selective factor 1''' (also known as '''SL1''') is a [transcription factor](/source/transcription_factor) that binds to the [promoter](/source/gene_promoter) of [gene](/source/gene)s and recruits a preinitiation complex to which [RNA polymerase I](/source/RNA_polymerase_I) will bind to and begin the transcription of [ribosomal RNA](/source/ribosomal_RNA) (rRNA).<ref name="pmid10082553">{{cite journal | vauthors = Tuan JC, Zhai W, Comai L | title = Recruitment of TATA-binding protein-TAFI complex SL1 to the human ribosomal DNA promoter is mediated by the carboxy-terminal activation domain of upstream binding factor (UBF) and is regulated by UBF phosphorylation | journal = Molecular and Cellular Biology | volume = 19 | issue = 4 | pages = 2872–9 | year = 1999 | pmid = 10082553 | pmc = 84080 | doi = 10.1128/MCB.19.4.2872 }}</ref><ref>{{cite book |url={{Google books | plainurl=yes | id = yXFfPkLq4yEC | page = 555 }} | title=Lewin's Genes XI |publisher= |date= |accessdate=2014-08-10}}</ref>

== Discovery ==
SL1 was discovered by [Robert Tjian](/source/Robert_Tjian) and his colleagues in 1985 when they separated a [HeLa cell](/source/HeLa_cell) extract into two functional fractions.<ref name="pmid12782648">{{cite journal | vauthors = Hochheimer A, Tjian R | title = Diversified transcription initiation complexes expand promoter selectivity and tissue-specific gene expression | journal = Genes & Development | volume = 17 | issue = 11 | pages = 1309–20 | year = 2003 | pmid = 12782648 | doi = 10.1101/gad.1099903 | doi-access = free }}</ref> One factor has RNA polymerase I activity, but no ability to initiate accurate transcription of a human rRNA template. This transcription factor, SL1, showed species specificity.<ref name="pmid8552083">{{cite journal | vauthors = Hempel WM, Cavanaugh AH, Hannan RD, Taylor L, Rothblum LI | title = The species-specific RNA polymerase I transcription factor SL-1 binds to upstream binding factor | journal = Molecular and Cellular Biology | volume = 16 | issue = 2 | pages = 557–63 | year = 1996 | pmid = 8552083 | pmc = 231034 | doi = 10.1128/MCB.16.2.557 }}</ref>  That is, it could distinguish between the human and mouse rRNA promoter,<ref>{{cite book | url = {{google books |plainurl=yes |id=jnTEbintTj0C | page=110 }} |title=The Nucleolus |publisher= |date=2011-09-15 |accessdate=2014-08-10}}</ref> and added increasing amount of human template at the expense of the mice template.<ref name="pmid3929071">{{cite journal | vauthors = Learned RM, Cordes S, Tjian R | title = Purification and characterization of a transcription factor that confers promoter specificity to human RNA polymerase I | journal = Molecular and Cellular Biology | volume = 5 | issue = 6 | pages = 1358–69 | year = 1985 | pmid = 3929071 | pmc = 366865 | doi = 10.1128/MCB.5.6.1358 }}</ref> Tijian and coworkers went on to show that by [footprinting](/source/DNA_footprinting) a partially purified polymerase 1 preparation could bind to the human rRNA promoter. In particular it causes a footprint over a region of the UCE called ''A site''.<ref>{{cite web| url=https://patents.google.com/patent/US5637686 |title=Patent US5637686 - Tata-binding protein associated factor, nucleic acids - Google Patents |date= |access-date=2014-08-10}}</ref> This binding is not due to polymerase I itself but to a transcription factor called upstream binding factor, [UBF](/source/UBTF).

== Function ==
SLI functions in assembling the [transcription preinitiation complex](/source/transcription_preinitiation_complex). It is also a major determinant of species-specificity in ribosomal RNA gene transcription. Research suggests that UBF and SL1 act synergistically to stimulate transcription. Recent investigation also suggests that SL1 is a target for [cancer therapy](/source/cancer_therapy).<ref name="pmid24576043">{{cite journal | vauthors = Villicaña C, Cruz G, Zurita M | title = The basal transcription machinery as a target for cancer therapy | journal = Cancer Cell International | volume = 14 | issue = 1 | article-number = 18 | year = 2014 | pmid = 24576043 | pmc = 3942515 | doi = 10.1186/1475-2867-14-18 | doi-access = free }}</ref>

== Structure ==
SL1 is composed of the [TATA-binding protein](/source/TATA-binding_protein) and at least four TAF (TATA box-binding protein-associated factor) subunits ([TAF1A](/source/TAF1A), [TAF1B](/source/TAF1B),[TAF1C](/source/TAF1C) and [TAF1D](/source/TAF1D)).<ref name="pmid15970593">{{cite journal | vauthors = Friedrich JK, Panov KI, Cabart P, Russell J, Zomerdijk JC | title = TBP-TAF complex SL1 directs RNA polymerase I pre-initiation complex formation and stabilizes upstream binding factor at the rDNA promoter | journal = The Journal of Biological Chemistry | volume = 280 | issue = 33 | pages = 29551–8 | year = 2005 | pmid = 15970593 | pmc = 3858828 | doi = 10.1074/jbc.M501595200 | doi-access = free }}</ref> It is therefore possible to inhibit SL1 activity with anti-TBP antibodies.

==See also==
* [RNA polymerase I](/source/RNA_polymerase_I)
* [RNA polymerase III](/source/RNA_polymerase_III)
* [Transcription preinitiation complex](/source/Transcription_preinitiation_complex)
== References ==
{{Reflist}}
Category:Transcription factors

---
Adapted from the Wikipedia article [Selective factor 1](https://en.wikipedia.org/wiki/Selective_factor_1) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Selective_factor_1?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.