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Selective factor 1 (also known as SL1) is a
Selective factor 1 (also known as SL1) is a transcription factor
In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
that binds to the promoter of gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
s and recruits a preinitiation complex to which RNA polymerase I
RNA polymerase 1 (also known as Pol I) is, in higher eukaryotes, the polymerase that only transcribes ribosomal RNA (but not 5S rRNA, which is synthesized by RNA polymerase III), a type of RNA that accounts for over 50% of the total RNA synthesiz ...
will bind to and begin the transcription of ribosomal RNA
Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal ...
(rRNA).
Discovery
SL1 was discovered by Robert Tjian and his colleagues in 1985 when they separated a HeLa cell extract into two functional fractions. 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. That is, it could distinguish between the human and mouse rRNA promoter, and added increasing amount of human template at the expense of the mice template. Tijian and coworkers went on to show that by 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''. This binding is not due to polymerase I itself but to a transcription factor called upstream binding factor, UBF.Function
SLI functions in assembling thetranscription preinitiation complex
The preinitiation complex (abbreviated PIC) is a complex of approximately 100 proteins that is necessary for the transcription (genetics), transcription of protein-coding genes in eukaryotes and archaea. The preinitiation complex positions RNA po ...
. 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
Cancer treatments are a wide range of treatments available for the many different types of cancer, with each cancer type needing its own specific treatment. Treatments can include surgery, chemotherapy, radiation therapy, hormonal therapy, targe ...
.
Structure
SL1 is composed of theTATA-binding protein
The TATA-binding protein (TBP) is a general transcription factor that binds to a DNA sequence called the TATA box. This DNA sequence is found about 30 base pairs upstream of the transcription start site in some eukaryotic gene promoters.
T ...
and at least four TAF (TATA box-binding protein-associated factor) subunits ( TAF1A, TAF1B, TAF1C and TAF1D). It is therefore possible to inhibit SL1 activity with anti-TBP antibodies.
See also
*RNA polymerase I
RNA polymerase 1 (also known as Pol I) is, in higher eukaryotes, the polymerase that only transcribes ribosomal RNA (but not 5S rRNA, which is synthesized by RNA polymerase III), a type of RNA that accounts for over 50% of the total RNA synthesiz ...
* RNA polymerase III
In eukaryote cells, RNA polymerase III (also called Pol III) is a protein that transcribes DNA to synthesize 5S ribosomal RNA, tRNA, and other small RNAs.
The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose ex ...
* Transcription preinitiation complex
The preinitiation complex (abbreviated PIC) is a complex of approximately 100 proteins that is necessary for the transcription (genetics), transcription of protein-coding genes in eukaryotes and archaea. The preinitiation complex positions RNA po ...
References
{{Reflist Transcription factors