Cell differentiation 2

what is a TATA box

a DNA signal sequence that binds TATA binding protein

what are enhancers recognised and interpreted by

proteins called transcription factors which are cell type specific

what happens if a transcription factor is present in a cell

it binds its DNA signal, this can activate or repress RNA polymerase function, the gene is therefore switched on of off for transcription

what does a genes transcriptional activity in a cell depend on

what binding sites are in its DNA enhancer sequences, whether the corresponding TFs are present in the cell

how can transcription factors act

they can directly recruit RNA polymerase to the TATA box or they may indirectly recruit RNA polymerase by altering chromatin structure

what does histone acetyl transferase do

acetylation loosens histone interaction with DNA, making the gene more accessible

what is the process of muscle cell differentiation

starts as mesoderm, then becomes somites, then myotome which contains the precursors to muscles, they don’t differentiate immediately after this

what happens once the myotome cell type is reached in muscle differentiation

in the early embryo, the myoblasts proliferate to increase their number because surrounding tissues secrete growth factors that promote myoblast proliferation, later on in development, the surrounding tissues stop secreting growth factors which stop the myoblasts from proliferating, triggering cell differentiation

what is a key transcription factor for muscle cell differentiation and what does it activate

MyoD, it activates expression of the gene form muscle myosin II

describe MyoD

it acts as a dimer, has a basic helix loop helix domain, binds to DNA as a protein dimer, recognition sequence known as an E box

which genes are some that have MyoD, E box recognition sequence

muscle myosin II, troponin, tropomyosin

what happens in muscle development of MyoD KO mice

cell lineage progression is blocked

what are the three key areas in which transcription factors are analysed

expression pattern, loss of function, gain of function

how is loss of function tested for transcription factors, what is the question we are trying to answer

is the transcription factor required for cell differentiation, mutate the gene encoding the transcription factor

how is gain of function analysed in transcription factors, what is the question we are trying to answer

can the transcription factor force cell differentiation, express it in cells that don’t normally have the factor

what are plant leaf trichomes and what is their function

hair like structures, deter insect, break up wind currents, and reduce sun exposure

what mutation affects the gene encoding a transcription factor for trichomes

glabra1

how do transcription factors recognise their DNA binding sites

they have a DNA binding domain which is forced into the major groove in the double helix, then binds to the DNA sequence that contains the target sequence through hydrogen bonds, they can only bond with correct base pairs

do transcription factors usually work alone or in combinations

in combinations

when transcription factors are repressors, how do they act

prevent binding of activators or recruit proteins that tighten chromatin, making the gene less accessible

what is the main transcription factor involved in RBC differentiation

GATA1

what type of transcription factor is GATA1

zinc finger

what does GATA1 bind to

GATA

what do KOs of mouse GATA1 gene do

cause anaemia due to death of erythroid precursor cells

what are the target genes of GATA1

alpha and beta globin genes, erythropoietin receptor, haem biosynthesis enzymes, spectrin

is GATA1 enough to activate transcription alone

no

what must be present with GATA1 for the transcription of the beta globin gene

NF1 and CP1

where does the beta globin gene have enhancers

both upstream and downstream

which binding site on the beta globin gene is more important and why

the upstream enhancer because it has binding sites for many other transcription factors

what cell types does GATA1 activate globin genes in

only in erythroblasts

what do human mutations of GATA1 result in

anaemia and blood clotting disorders