*Gene Expression II

Question 1

SW1/SNF complexes

Answer 1

Chromatin remodeling complexes that promote:

1) sliding - histone octamers slide along DNA to new positions (exposes TATA box)
2) conformational change - form transient loop that makes site more accessible for regulatory proteins (exposes TATA box)

Question 2

SWR1 complex

Answer 2

Chromatin remodeling complex that replaces histone core octamer with a variant that is correlated with active transcription

Question 3

FACT complex

Answer 3

Chromatin remodeling complex that displaces octamer from DNA

Question 4

HIGH level of histone H1: ___ active transcription

Answer 4

No

Question 5

X-Chromosome Inactivation Center (XIC)

Answer 5

when it is methylated, generates a non-coding RNA that specifically targets and inactivates the entire X-chromosome that it is on (Lyon hypothesis, calico cats)

Question 6

_______ promotes epigenetic methylation (silencing) of genes that cause cancer

Answer 6

Folate, B12
Folate plays an essential role in remethylation of homocysteine to methionine, thereby ensuring the provision of S-adenosylmethionine, the primary methyl group donor for most biological methylation reactions.

Question 7

______ reduces epigenetic methylation (silencing) of genes that cause cancer

Answer 7

Ethanol

Question 8

Riboswitches

Answer 8

bacterial mRNAs can bind to a small metabolite in their 5’ UTR, which alters the gene involved in producing that metabolite.
Block either termination of transcription or initiation of translation.

Question 9

miRNA

Answer 9

Regulatory role in development
patterning of the nervous system
control of cell proliferation and cell death
leaf/flower development in plants
differentiation of cells
roles for miRNAs in development of cancer
synthesized in specific tissues during embryonic development
*form double stranded RNA with stem loop on one end

Question 10

RNAi

Answer 10

produced when a double stranded RNA shares the same sequence as the target mRNA, and results in the destruction of the mRNA.

Question 11

How is translation of lin-14 mRNA repressed?

Answer 11

noncoding miRNAs from lin-4 bind to it and silence its expression

Question 12

Acetylation of H3/H4 Lys leads to:

Answer 12

Acivation

Question 13

Methylation of Me-H3K9, Me-H3K27 leads to:

Answer 13

Repression

give a dog meth = tranquilizes it, 27 is a multiple of 9

Question 14

Methylation of Me-H3K4, Me-H3K36

Answer 14

Activation

Milly, 4, and Mom, 36, are very active

Question 15

Epigenetic

Answer 15

Inheritance not coded in DNA

Changing expression without changing DNA

Question 16

Euchromatin

Answer 16

• the ON chromatin state with decondensed chromatin and easy access to transcription machinery.
• is hyperacetylated and enriched in H3 K4 methylation.
• Trithorax group proteins maintains this^, catalyzed by MLL

Question 17

________ is hypoacetylated and enriched in H3 K9 methylation and H3 K27 methylation

Answer 17

Heterochromatin

polycomb group proteins maintain H3 K27 methylation, catalyzed by EZH2.

Question 18

To convert euchromatin to heterochromatin:

Answer 18

Remove acetyl groups from H3 and H4 histones.
Then methylation of H3K9 methyltransferase (SUV39H1)
Methylated H3K9 binds to chromodomain (HP1)
HP1-HP1 interactions facilitate chromatin packaging

Question 19

Coactivators

Answer 19

Act as intermediates for transcription factors
class 1) interact with transcription machinery
class 2) alter chromatin structure, using HATS, or remodeling complexes

Question 20

How do you turn off gene expression?

Answer 20

• reducing the levels of TF activators to change the balance between activators/repressors, reducing everything to basal levels of expression
• often accompanied by the shift from euchromatin to heterochromatin

Question 21

HATs

Answer 21

add acetyl groups to chromatin; activation

Question 22

HDACs

Answer 22

histone deacetylaces - remove acetyl groups from chromatin; repression.
-subunits of larger complexes: corepressors

Question 23

Corepressors

Answer 23

Recruited by TFs to specific gene loci that cause the gene to be silenced.

Question 24

Corepressor Complexes:

Answer 24

SMRT/N-CoR or CoREST

Question 25

XIST RNA

Answer 25

selectively accumulates along the length of the X chromosome from which it is transcribed, where it helps recruit certain protein complexes that inactivate the genes at selected sites. (Lyon hypothesis)

Question 26

Genomic Imprinting

Answer 26

• epigenetic phenomenon by which certain genes are expressed in a parent-of-origin-specific manner.
• result of selective DNA methylation of certain regions that control the expression of either the male or female alleles.
• imprinted gene is not expressed (?)
• caused by DNA methylation on cytosine

Question 27

Unmethylated promotor: E Globin gene ______

Answer 27

Active

Question 28

S-adenosylmethionine

Answer 28

the primary methyl group donor for most biological methylation reactions