transcription factors.txt

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What is transcription factor?
- proteins that contain DNA binding domains
- binds to DNA at specific sequences next to genes they regulate
- Involved in regulating TRANSCRIPTION of DNA to RNA
Role of General transcription factors and co-factors
- Help RNA polymerase II in transcriptional process
- Needed to form initiation competent RNA polymerase complex
Experiment performed to see bio significance of GTF's
- pol. II with subcellular fractions able to transcribe DNA template
- Purification of subcellular fractions showed protein factors required for pol. II mediated transcription
- These protein factors named TFIIA and TFIID
Role of TFIID
- made of TBP (TATA binding protein) and 13 associated factors (TAFs)
- TAF subunits MEDIATE transcriptional regulation thru interacting w/other co-reg. proteins
Role of TFIIA
- 1. Stimulates transcription by:
- a. STABILIZING TBP binding to TATA box and
- b. REGULATING TBP or TFIID dimerization to ACCELERATE DNA binding
- 2. Reverses INHIBITORY effects of negative co-factors
- 3. Necessary for basal and activated transcription from TATA-less promoters
- 4. Acts as co-activator and enhances the effects of activators
Cleavage of TFIIA
- Taspase I cleaves into TFII alpha and beta
- Alpha and beta play a role in protease dependent degradation
- Regulates subset of genes such as cell cycle-related genes
- Involved in BULK transcription and overlap with function of uncleaved TFIIA
- Cleavage NOT step required for activation, as uncleaved can support BULK transcription
Core promoter elements recognized by TFIID
- 7 core promoter elements required for promoter initiation complex (PIC)
- These promoter elements aid in:
- 1. promoter function
- 2. proper assembly and
- 3. orientation of PIC
- Initiator recognized by TAF2 components of TFIID
- TFIIB recog. BRE and helps orient DIRECTION of PIC
- Rate of assembly of complexes (pol II, TFIIB and F) DECREASED by TAF subunits of TFIID (TFIIA and TFIID binding to promoter)
- FYI: Pol II contacts large region of promoter DNA
Role of TBP
- Recognizes TATA box - interacts directly with DNA
- TATA Box aids in initiation of PIC assembly through TATA containing promoters
- Causes bend in DNA allowing regulatory factor connection with basic transcription factors (bent structure forms a loop-like structure with all 3 components)
TATA box binding interactions with DNA
- Lysine and Arginine side chains bind to Phosphate backbone of DNA
- Cause conformational change
Role of TAF1
- Responsible for downstream protection with TFIID
- Largest of all 16 factors of TFIID
- Extends from promoter to initiation site
- Involved with ACETYLTRANSFERASE activity
- Role in Interaction with ACTIVATOR
- Kinase on N terminus and C terminus add phosphate to GTFs and TAFs
Phosphates and TBP & TAF

Adding phosphates can INHIBIT Transcription during pro-metaphase
TAF2

Provides stability to TFIID complex

Author

rincrocci

143725

Card Set

transcription factors.txt

Description

transcription factors

Updated

3/25/2012, 9:32:14 PM

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