10. Ras Dependent Signaling Pathways

Question 0

reverse transcriptase

Answer 0

synthesizes DNA from RNA

mechanism of a retrovirus

Question 1

retrovirus

Answer 1

RNA virus whose genome consists of 2 identical copies of RNA that are base paired to tRNA

contain reverse transcriptase that allows the single-stranded RNA viral genome to be synthesized into a DNA strand that is complementary to the viral DNA

Question 2

what does integrase do?

Answer 2

facilitates the integration of the double-stranded viral DNA into the nucleus & host genome

Question 3

3 genes in a retrovirus?

Answer 3

gag
pol
env

Question 4

what do LTRs do?

Answer 4

LTR=long terminal repeat

facilitate the integration of the viral chromosome into the hose DNA; contain promoters that drive viral gene expression

Question 5

what do src encode?

Answer 5

tyrosine kinase

Question 6

what is src (tyrosine kinase)’s role?

Answer 6

cell division
cell-cell interactions
intracellular comunication

Question 7

c-src gene

Answer 7

native proto-oncogene

will cause cancer if mutated

Question 8

v-src gene

Answer 8

oncogene located in a retrovirus

Question 9

defective viruses need?

Answer 9

helper virus

Question 10

what do helper viruses do?

Answer 10

they provide gag, pol, and/or env to allow the defective virus to replicate

Question 11

monomeric G proteins are equivalent to?

Answer 11

the alpha subunit of trimeric G proteins

Question 12

monomeric G protein function?

Answer 12

have GTPase activity

involved in cell signaling & growth

Question 13

what accounts for 30% of all cancers?

Answer 13

activating mutations of c-ras

Question 14

c-ras signaling involves (3 things)

Answer 14

1. GTP-binding proteins with high affinity
2. slow GTPase activity
3. slow GDP dissociation

Question 15

ras-GDP =

Answer 15

inactive

Question 16

ras-GTP=

Answer 16

active

Question 17

how do monomeric & trimeric G protein differ?

Answer 17

monomeric: GTPase slower to activate & slower to inactivate

Question 18

what do monomeric & trimeric G protein have in common?

Answer 18

slow rate of GDP dissociation

Question 19

ras is regulated by what 2 accessory proteins?

Answer 19

GAP & GEF

Question 20

GTPase Activating Protein (GAP) function?

Answer 20

turns off ras

by accelerating intrinsic GTPase activity of c-ras
by activating GTPase, you inhibit ras via GTP hydrolysis

Question 21

guanine nucleotide exchange factor (GEF) is also called..

Answer 21

guanine nucleotide releasing protein (GNRP) or guanine nucleotide exchange protein (GNEP)

Question 22

what does GEF do?

Answer 22

activate ras

by accelerating GDP dissociation from c-ras
(activates by stimulating the rate-limiting step of GDP dissociation, turning ras on)

Question 23

ras is also regulated by?

Answer 23

guanine nucleotide dissociation inhibitors (GDI)

Question 24

what do GDIs do?

Answer 24

stabilize the c-ras GDP state

prevents rate-limiting step of GDP dissociation from occurring, ensuring ras is off

Question 25

ras is stimulated by?

Answer 25

1. inhibition of GAP
2. activation of GEF
3. inhibition of GDI

Question 26

what is rho?

Answer 26

subfamily of the ras superfamily of GTPases

Question 27

what is Rho’s function?

Answer 27

involved in cytoskeleton organization through serine-threonine protein kinases

Question 28

rho’s relationship w/GEF & GAP & GDI?

Answer 28

GEF: stimulates GDP dissociation (activating)
GAP: turns Rho off
GDI: stabilizes inactive Rho

Question 29

what does the MAP kinase cascade do?

Answer 29

activates a mitogen

Question 30

what does a mitogen do?

Answer 30

simulate growth & cell division

Question 31

MAP kinase cascade

Answer 31

map kinase-kinase-kinase-kinase -->
map kinase-kinase-kinase -->
map kinase-kinase -->
map kinase -->
enter nucleus, phosphorylate transcription factors

Question 32

Raf

Answer 32

effector molecule of Map-kinase cascade

Question 33

scaffold proteins

Answer 33

hold together proteins in the cytoplasm that function as binding sites for all components of a MAP kinase cascade

serve as regulators, help maintain selectivity

Question 34

what does MAP kinase do when ras is activated

Answer 34

MAP kinase dissociates from the scaffold, enters the nucleus, activates a small set of TFs that regulate an activity

Question 35

what is the function of immediate early genes

Answer 35

function as primary response genes:
induce transcription within minutes of stimulation 
turn on independent protein synthesis 
shutoff dependent protein synthesis 
short mRNA half life (5-15mins)

Question 36

what do protein products of immediate early genes do? (2 things)

Answer 36

1. bind late response genes to turn them on
   OR
2. bind genes or mRNA of the immediate early genes to turn them off or degrade them

Question 37

characteristics of late response genes?

Answer 37

gene expression occurs after several hours

turn on dependent on protein synthesis

Question 38

what happens in the presence of inhibitors or protein synthesis?

Answer 38

early-response genes are not turned off and delayed-response genes are not turned on because there are NO protein product of the early response genes produced (which bind late response genes to turn on)