Cell differentiation 3

what is one of the most common post transcriptional modifications

phosphorylation

what is the result of phosphorylation of a protein

a change in conformation that results in a change in function

what are the two basic effects of phosphorylation on transcription factors

can either activate or inhibit the transcription factor

what type of enzyme is used to achieve phosphorylation

kinases

what does kinase do

transfers phosphate from ATP to another molecule

do proteins usually only have one phosphate group added during phosphorylation

no, proteins often have more than one phosphate group added

what does mitogen activated protein kinase do

promote mitosis by phosphorylating transcription factors

give an outline of a protein kinase cascade

Raf is activated by a protein network that happens in response to a signal binding the receptor, MAPKK is phosphorylated by Raf, which goes on to phosphorylate MAPK, this causes MAPK to translocate into the nucleus and phosphorylate a TF, the pathway ultimately results in the phosphorylation of a TF which is already present in the cell

what is EGF (epidermal growth factor)

a mitogen that promotes cell proliferation

what does binding to epidermal growth factor receptors result in

phosphorylation of MYC, which is phosphorylated on several serine and threonine residues, this stabilised MYC drives the transcription of cyclin genes

when is MYC often mutated

in cancers where it becomes too active and you get uncontrollable proliferation

what is erythropoietin (EPO)

a regulator of the rate of RBC production

where is EPO secreted from

the kidney

what does binding to EPO receptors on erythroblasts do

stimulate progenitor proliferation and erythropoiesis

what does EPO do to GATA1

causes phosphorylation, increasing DNA binding affinity

is unphosphorylated GATA1 still active

yes, but at a lower level

what do conditions of low oxygen stimulate in erythropoeisis

greater EPO secretion

what is the overall function of MyoD

to regulate muscle gene expression and coordinate activation of muscle target genes

where is MyoD expression limited to

only expressed in cells that are differentiating

what are transcription factor genes regulated by

transcription factors

what are stomata in simple terms

parts of the leaf that are specialised for gas exchange, the opening is controlled by osmosis in specialised guard cells

what type of channel proteins are important for regulation of the opening and closing of stomata

KAT1 potassium channel proteins

what are the steps that the protoderm leaf cell goes through to become a guard cell

protoderm, meristemoid mother cell, meristemoid cell, guard mother cell, guard cells

what type of cell forms the majority of the leaf epidermis

pavement cells

what are the three genes that causes stomata to be missing if they are mutated

SPCH, MUTE, FAMA

what transition doe SPCH allow

protoderm to meristemoid mother cell

what transition does MUTE allow

meristemoid to guard mother cell

what step does FAMA allow

the final differentiation into guard cells

what group of cells in the very early embryo do muscle cells come from

the paraxial mesoderm

what are the rough steps of muscle differentiation

mesodermal progenitor, myoblasts, multinucleate myotube, muscle fibre

what are the transcription factors that are involved in myogenesis

MyoD, Myf5, Mrf4, myogenin

what is the paired box homeodomain transcription factor expressed in somites

Pax3

what are the regulator signals involved in myogenesis

Wnt, SHH, BMP

which regulator signal starts of the process of myogenesis

SHH

which transcription factors must be present for MyoD to be activated

Myf5 and Pax3

what does Pax3 do in myogenesis

tells somites that they must respond to SHH

what does the positive autoregulation of MyoD mean

MyoD activates its own expression (positive feedback loop)

why does MyoD expression eventually become independent of Myf5 and Pax3

because MyoD activates its own expression

what phosphorylates MyoD and Myf5

cyclin-dependent kinase

what happens to muscle proliferation while growth factors are present

muscle differentiation is inhibited and myoblast proliferation is enhanced

what is the effect of phosphorylation on MyoD

it destablises it, preventin muscle differentiation

how is Pax3 mRAN degraded

by RNA interference from a specific regulatory RNA called microRNA miR-1

how does miR-1 work

part of it is complementary to the MyoD mRNA causing the degradiation of the Pax3 mRNA, Pax3 eventually disappears as it is a relatively unstable protein