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