8-20 Gene Xpress EPIGENETIC Inheritance

Question 0

What does tx factor [Myc] do?

Answer 0

Myc Heterodimerizes w/other bHLH-ZIP proteins

Question 1

Combinatorial Tx Regulation

Answer 1

Eukaryotes regulate gene tx through the binding of MULTIPLE tx factors to a regulatory gene element

Question 2

[Myc-Max] tx factor combo

Answer 2

[Myc-Max]= dimers that induce cell proliferation/division and activates tx when bound to E-box element of a gene

Question 3

[Mad-Max] tx factor combo? [3]

Answer 3

[Mad-Max]= dimers that…

• STOP cell proliferation,
• represses tx
• and instead START cell differentiation when bound to E-box element of a gene

Question 4

1) [Myc-Max] and [Mad-Max] complexes have ____ functions during tx and _____ plays the central role for this
2) All of these tx factors bind to the _____ of a gene to affect it?

Answer 4

1) Myc-Max and
Mad-Max have OPPOSITE functions during tx and MAX PLAYS THE CENTRAL ROLE FOR WHY! “Oh max smh…”

2)ALL of these tx factors bind to the “E-box Element” of a gene when affecting it

Question 5

1) Which tx factor between Myc, Max and Mad is continuously expressed?
2) What is special about this tx factor?

Answer 5

1) MAX is continuously expressed

2) soo….[[Max-Max]] together will SILENCE TRANSCRIPTION when bound to E-box element of a gene

Question 6

Which tx factor between Myc, Max and Mad is ONLY EXPRESSED during the G1–>S transition in the cell cycle?

Answer 6

[Myc] is ONLY EXPRESSED during the G1–>S transition in the cell cycle

Question 7

1) What are c-Jun and c-Fos?
2) What do they do?

3)How are they formed?

Answer 7

1) bZIP proteins that heterodimerize thru leucine zippers and then binds to AP-1 element w/ a scissor motif———>
2) [with the addition of tx actor ETS] activates cancerous metastasis genes

3)Upstream: AP-1 element binds to tx factors c-Jun(activated by JNK kinase) and then tx factor c-Fos(activated by ERK kinase)–>to just have them togethr bind to scissor motif of the AP-1 element within the gene regulatory region

Question 8

1) [T or F] The actual location of a Gene in heterochromatin or euchromatin of a chromatid will influence that genes expression….
2) How is this?

Answer 8

1) TRUE!

2) Placing a Gene into conDensed/Heterochromatin will STOP that genes expression

Question 9

Histone DeAcetylation ____[opens/condenses] Chromatin Structure!

Answer 9

Histone DeAcetylation conDenses Chromatin Structure—–>

—>Turns Chromatin into Heterochromatin!

Question 10

1)Females sex chromosomes are ___. Explain how 1 of those
__-chromosomes are inactivated in female cells

2)What is this also called?

Answer 10

1) Female = XX.–> 1 of these X-chromosomes is inactivated in early embryo by RANDOM CONDENSATION–> which is then a condensation conferred to all of her gametes afterward!
2) Clonal inheritance

Question 11

1) Define Epigenetic
2) How does Epigenetic mechanisms occur?

3)What’s the “catch” regarding Epigenetics?

Answer 11

1) Epigenetics =inheritance/information passed from Parent to progeny by a mechanism DIFFERENT than the instructions found in the base seq. of copied DNA
2) Epigenetics happen when outer DNA or gene regulatory proteins are modified (but not the base sequence of DNA itself)
3) Because of Epigenetics-2 alleles can have exact same nucleotide sequences but still give DIFFERENT inheritable genetic information for the progeny

Question 12

What are the 4 types of Epigenetic Mechanisms?

Answer 12

1. Positive Feedback Transcription factor Loops (self-activation)
2. DNA methylation
3. acetylation and DeAcetylation/conDense of histones (euchromatin and Heterochromatin)
4. Histone Phosphorylation and Histone Methylation

Question 13

How does the Epigenetic mechanism:

[Positive Feedback Tx factor loop] create “cellular memory”

Answer 13

1. When a protein (Protein A for ex) is only tx because of ITSELF acting as the promoter it takes a “TRANSIENT SIGNAL” to initially startup the expression of protein A since they’ll be none floating around yet.
2. Once transient signal starts up Protein A expression, the memory of what that transient signal did is “rememberd” by all the cell’s descendants—>Protein A expression in the descendants as well

Question 14

1) Methylated DNA sequences have to be _________

2) How does DNA methylation affect gene expression?

Answer 14

1) Methylated DNA sequences are always PALINDROMIC

2) DNA methylation of a gene promoter or enhancer region USUALLY INHIBITS gene expression

Question 15

Explain the mechanism for passing DNA methylation from parent to progeny cells [4]

Answer 15

1) Initially, Both strands are methylted in parental cells
2) Progeny cells at first will have hemi-methylated sites from the parent but..>{only template strand is methylated/not the daughter strnd}

3)…soo Maintenance-Methylase enzyme [apart of progeny cell] finds
non-methylatd sites on daughtr strand and converts the hemi-met DNA into FULLY methylated & PALINDROMIC site {{both strands methylated}}
4)Now progeny has same methylated C-sites has parent

Question 16

Why is DNA methylation MORE LIKELY to occur on cells that no longer make required activator proteins “old cells”?

Answer 16

Gene regulatory proteins and tx machinery near an actual ACTIVE promoter will stop DNA methylation from occuring by obstruction. If these activator proteins weren’t here consistently–>methylase enzymes could swoop onto tht DNA and methylate it shutting dwn the gene thru its structural chnge

Question 17

How are Acetylated Histone regions passed on from parent cell to progeny cell?

Answer 17

Maintenance acetylases of the progeny cell, acetylate nucleosome histone proteins that are only hemi-acetylated at first. When complete, THE SAME acetylated regions from chromatin of parent cell will also be able to be found in the progeny cell as well

Question 19

1) What is Genomic imprinting?

2) Why does it occur in a sex-dependent manner?

Answer 19

1) RETAINING Egg/Sperm DNA regulatory element methylation on “special” genes even when MAJORITY of methyl groups for regulatory elements of MOST OTHER genes are removed/genes recycled!
- ->occurs in about 50 “special” human genes

2) Sex-Dependent becuz a specific gene which retains its methylation in a sperm CAN NOT ALSO retain its methylation when in an egg[its methylation can only occur in sperm for tht gene]
- —>Non-mendelian genetic xpression of imprinted genes

Question 20

MAPK

Answer 20

ULTIMATE FINAL Kinase in any signal pathway which phosphorylates Tx fActors –>Gene Xpression finally lol

Question 21

LCR (Locus Control REgion)

2)Where is this region usually found?

Answer 21

Controls the expression of 5 diff globin(hemoglobin) genes which are expressed in different parts of human life
[E, G, A, S and B]
2)LCR usually found in heterochromatin but is in EUCHROMATIN in RBC!

Question 22

Self-Activation (AKA_____________) is a _____Mechanism

Answer 22

Self-Activation (Positive feedback transcription factor loop) is an EPIGENETIC MECHANISM