L15 - regulation of eukaryote gene expression Flashcards
what are housekeeping genes
genes constitutively expressed in all cells
eg respiration genes
why do Eukaryotes show greater regulation of genes than prokaryotes
- different cell types + function
- need to respond to environment
- need genes at different times eg embryo vs adult
are there operons in eukaryotes?
no
all genes are regulated individually
list the stages at which E genes can be regulated
- transcription (promoters, methylation)
- mRNA processing (splicing, 5’ capping)
- mature mRNA regulation (stability in cytosol)
- translation / post translational (golgi)
where is a promoter region for a gene located?
upstream 5’ end
what is found in a E promoter region
- core promoter sequence
- regulatory promoter sequence
RNA pol 1+3 function
transcribe
- tRNA
- rRNA
- some small nRNA
RNA pol 2 function
transcribes protein coding genes (and some non coding RNA)
role of core promoter region?
directs DNA pol to start of T
where is regulatory promoter region
upstream 5’ to the core promoter region
role of regulatory promoter region
sequence is recognised by regulatory transcription factors that activate / repress T
what can general T factors bind to
all promoters
what are the names of general T factors?
TF2A , TF2B etc
role of general T factors
- position RNA at start of transcription
- help separate DNA strands for T
what is the name of the complex formed by T factors and promoter
pre - initiation complex
what is TBP?
important T factor
TATA binding protein
forms part of TF2D complex
where does TBP bind to on DNA?
the TATA sequence of promoter in minor groove
explain process of pre-initiation complex formation (TBP)
- TBP binds to TATA sequence on core promoter forming TF2D complex
- this bends the DNA allowing other TFs to bind
- RNA pol recognises the complex and binds to it in the correct place for T
where do regulatory TFs bind and what is their function
bind to regulatory region
activate/repress T
what is found in the regulatory region
- CAAT box
- GC box
what binds to CAAT box of regulatory region
CBP
CAAT box binding protein
what binds to GC box of regulatory region
SPI
role of SPI and CBP
activate basal level of Tscription
how do extra RTF’s alter transcription
form Tscription complexes, bind to regulatory regions upstream of GC box etc and :
-interact with pol2 /general TFs
-fold DNA
-
how do TFs bind to DNA (general)
have different DNA binding domains that form different AA - base interactions with DNA
what are enhancers?
sequences involved in regulating tissue/time/environmentally specific translation
describe enhancers
- can be up/downstream
- can be close / far away from T start site
- 200 b.p
- contain several TF binding sites
- interact with core/reg complex
- bend DNA
what is a mediator
protein complex that links upstream bound TFs (eg at enhancer) to core complex
define cis acting sequence
regulate transcription of adjacent gene (same chrom)
what binds to enhancers and what do they do?
regulatory proteins
interact with the core complex
what are trans acting regulatory proteins
bind to target sequence on any chrom
eg RNA pol 2
do all E genes only have 1 promoter?
no
some have several and so have several T start sites
can produce many transcripts from one gene
define heterochromatic
non transcribed regions of DNA (inactive)
define euchromatic
transcribed regions of DNA (active)
