transcription factors.txt

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  1. 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
  2. Role of General transcription factors and co-factors
    • Help RNA polymerase II in transcriptional process
    • Needed to form initiation competent RNA polymerase complex
  3. 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
  4. 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
  5. 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
  6. 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
  7. 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
  8. 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)
  9. TATA box binding interactions with DNA
    • Lysine and Arginine side chains bind to Phosphate backbone of DNA
    • Cause conformational change
  10. 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
  11. Phosphates and TBP & TAF
    Adding phosphates can INHIBIT Transcription during pro-metaphase
  12. TAF2
    Provides stability to TFIID complex
Card Set
transcription factors.txt
transcription factors
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