Transcript Transcription Coactivator Family Proteins

Transcription Co-activator Family Proteins
Combiz Richard Abdolrahimi
06-09-2005
HC 70AL Gene Discovery Lab
Dr. Bob Goldberg
UCLA/HHMI Institute
What are the Structures of RNA and DNA?
What is Transcription/Transcription Factors?
•
Transcription Factors: Any
protein required to initiate or
regulate transcription
•
RNA Polymerase II
Transcription factor activityenhancer binding, functions to
initiate or regulate RNA
polymerase II by binding a
promoter or enhancer region of
DNA
During transcription, mRNA is synthesized following the
sequence of nucleotides in the coding strand of DNA.
This will require the enzyme RNA polymerase and
nucleotides from which RNA will be constructed. RNA
polymerase will unwind the DNA, separate the strands,
and assemble the mRNA molecule using the coding
strand of DNA as a template.
TATA BOX & Function of
Transcription Co-Activators
• When a protein binds to a promoter, it automatically activates
transcription?
Not entirely, it needs the help of transcription coactivators
Stop
Regulating when/where gene is transcribed
Stop
TATA Box
3’ UTR
5’ UTR
Promoter of the Gene:
“On Switch”
3’ UTR
Hypothetical Example of the influence of Transcription Co-Activators
Structure of the upstream region of a typical eukaryotic
mRNA gene that hypothetically contains 2 exons and a
single intron. The diagram indicates the TATA-box and
CCAAT-box basal elements at positions -25 and -100,
respectively. The transcription factor TFIID has been
shown to be the TATA-box binding protein, TBP. Several
additional transcription factor binding sites have been
included and shown to reside upstream of the 2 basal
elements and of the transcriptional start site. The
location and order of the variously indicated transcription
factor-binding sites is only diagrammatic and not
indicative as being typical of all eukaryotic mRNA genes.
There exists a vast array of different transcription
factors that regulate the transcription of all 3 classes of
eukaryotic gene encoding the mRNAs, tRNAs and rRNAs.
What do Transcription Co-activators do? Why
are they important?
•
Transcription co-activators activate transcription from a RNA
polymerase II promoter, does not bind DNA itself
•
43 genes in the Arabidopsis Genome that have proteins that regulate
transcription
•
How do you know when/where your gene of interest is transcribed in
plants?
Activator proteins bind to genes known as
enhancers which help determine which genes are
switched on and speed up transcription.
Repressor proteins bind to genes called silencers
which interfere with activator proteins and slow
down transcription. “Co-activators, adapter
molecules which coordinate signals from activator
and repressor proteins, relay information to
basal factors which then tell RNA polymerase
where and when to start transcription.”
http://www.faculty.uaf.edu/ffdew2/geneticsWeb/lecture/lecture10.pdf
A Patent on Transcription Co-activator PC4
proteins
•
FIELD OF THE INVENTION
[0002] This invention is in the field of plant molecular biology. More specifically, this invention pertains to nucleic acid fragments encoding
PC4 transcription coactivators in plants and seeds.
BACKGROUND OF THE INVENTION
[0003] Activation of transcription in eukaryotes depends upon the interplay between sequence specific transcriptional activators and
general transcription factors. While direct contacts between activators and general factors have been demonstrated in vitro, an additional
class of proteins, termed coactivators, appear to be required for transcriptional activation of some genes. For example, transcription of
class II genes depends upon the assembly of basal transcription machinery containing RNA polymerase II and the general transcription
factors (GTFs): TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. Class II genes contain core-promoter elements recognized by the general
transcription factors and gene-specific sequences recognized by the activators. Coactivators mediate the interaction between the
transcriptional activators the GTFs. Transcription activation is the output of the interaction between the sequence-specific activator and
basal transcription machinery, which increases the efficiency and/or stability of the entire transcription machinery complex.
[0004] The positive cofactor 4 (PC4) functions as both an activator-dependent, and a general transcription factor-dependent coactivator. It
interacts with activation domains such as VP16 and the general transcription factors such as TFIIA, TFIIB, TFIIH and TAFs in TFIID. PC4
is a bridge or signal mediator between a set of specific activators and general transcription factors in transcription initiation complex (Wu
et al. (1998): EMBO J. 17:4478-4490; and Zhu et al. (1995) Plant Cell 7:1681-1689.) Positive Cofactor 4 has been purified from the
Upstream Stimulatory Fraction of HeLa cells and found to mediate activator dependent transcriptional activation. PC4 has been
demonstrated to be a promiscuous and potent coactivator interactng with several activators, including Ga14NP 16. PC4 itself is a nonspecific DNA binding protein that binds to both ssDNA and dsDNA, but has a higher affinity for ssDNA (Ge et al. (1994) Cell 78:513-523;
Henry et al. (1996) J. Biol. Chem. 271:21842-21847; Kaiser et al. (1995) EMBO J. 14:3520-3527; Kretzschmar et al. (1994) Cell 78:525534; and Werten et al. (1998) EMBO J. 5:5103-51 11. PC4 has also been shown to interact with members of the basal transcriptional
machinery. Specifically, the TFIIA-DNA and TFIIA-TFIIB-DNA complexes. Phosphorylation of PC4 by TFIIH or TATA associated factors
abolish PC4 DNA-binding activity. Additionally, PC4 and Ga14/VP 16 have been shown to be required during TFIID-TFIIA-DNA complex
formation (D-A complex) in order to stimulate transcription. This ability to affect D-A complex formation is linked to PC4's dsDNA-binding
characteristic.
•
www.freshpatents.com
Summary of Transcription Co-Activators in
Arabidopsis thaliana
•
Summary
•
Identification of transcription co-activators and factors are a
necessary prerequisite for the study of the molecular mechanisms of
gene activation in plants
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KIWI and KELP: 2 putative transcriptional co-activators from
Arabidopsis
•
Single-stranded DNA binding activity of PC4/p15 and all proteins
between 98 – 165 amino acids in length
•
Transcription factors include many protein families like MYBs and
…more
•
Research is currently being conducted to gather more information on
these pertinent co-activators