View source for Biology:Selective factor 1

{{Short description|Mammalian protein found in Homo sapiens}}
[[File:Role of transcription factor in gene expression regulation.svg|thumb|500px|Role of transcription factor in gene expression regulation]]
'''Selective factor 1''' (also known as '''SL1''') is a [[Biology:Transcription factor|transcription factor]] that binds to the promoter of [[Biology:Gene|gene]]s and recruits a preinitiation complex to which [[Biology:RNA polymerase I|RNA polymerase I]] will bind to and begin the transcription of [[Biology:Ribosomal RNA|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 and his colleagues in 1985 when they separated a 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 [[Biology:DNA footprinting|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://www.google.com/patents/US5637686 |title=Patent US5637686 - Tata-binding protein associated factor, nucleic acids - Google Patents |date= |accessdate=2014-08-10}}</ref> This binding is not due to polymerase I itself but to a transcription factor called upstream binding factor, UBF.

== Function ==
SLI functions in assembling the [[Biology:Transcription preinitiation complex|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.<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 | pages = 18 | year = 2014 | pmid = 24576043 | pmc = 3942515 | doi = 10.1186/1475-2867-14-18 | doi-access = free }}</ref>

== Structure ==
SL1 is composed of the [[Biology:TATA-binding protein|TATA-binding protein]] and three TAF (TATA box-binding protein-associated factor) subunits ([[Biology:TAF1A|TAF1A]], TAF1B, and TAF1C).<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==
* [[Biology:RNA polymerase I|RNA polymerase I]]
* [[Biology:RNA polymerase III|RNA polymerase III]]
* [[Biology:Transcription preinitiation complex|Transcription preinitiation complex]]
== References ==
{{Reflist}}
[[Category:Transcription factors]]

{{Sourceattribution|Selective factor 1}}