28.1 Proteins and RNAs of Gene Regulation

Question 1

Definition of Housekeeping Genes, example

Answer 1

Genes for products that are required at all times, for example enzymes in metabolic pathways.

Question 2

Definition of Constitutive Gene Expression

Answer 2

Expression of a Gene at approximately constant levels.

Question 3

Regulation of housekeeping genes

Answer 3

Strongly influenced by RNA polymerase - promoter interaction, and thus differences in a promoter may be the only level of regulation for these genes.

Question 4

The different types of RNAs and proteins that regulate transcription initiation

Answer 4

specificity factors, repressors, activators, ncRNAs (non-coding RNAs), and lncRNAs (long non-coding RNAs).

Question 5

Specificity factors

Answer 5

Proteins that increase specificity of RNA polymerase for promoter(s).

Question 6

Repressors

Answer 6

Protein that hinders access of RNA polymerase to promoter (keeps polymerase from binding).

Question 7

Activators

Answer 7

Protein that enhances the RNA polymerase - promoter interaction (easier binding).

Question 8

ncRNAs

Answer 8

Non-coding RNAs, RNAs that do not code for functional proteins.

Question 9

lncRNAs

Answer 9

Long non-coding RNAs, non-coding RNAs longer than 200 nucleotides.

Question 10

Bacterial specificity factor (with example)

Answer 10

Amino acid sequences that mediates promoter recognition and binding. The sigma subunit of RNA polymerase of E. coli, most promoters are recognized by the sigma 70.

Question 11

Eukaryotic specificity factors

Answer 11

Some of the general proteins involved in transcription may be seen as specificity factors, for example the TATA binding protein (TBP).

Question 12

Operators

Answer 12

Binding site for repressors, usually located near promoter

Question 13

Effectors

Answer 13

Molecules or proteins that affects how repressor (or activator) binds to DNA, induces conformational change.

Question 14

Negative regulation

Answer 14

Regulation by repressors

Question 15

Differences in repressors between bacteria and eukaryots

Answer 15

Negative regulation is less common in eukaryots, except lower eukaryots like yeast, the binding-site for repressors in eukaryots may be farther from the promoter than in bacteria.

Question 16

Positive regulation

Answer 16

Regulation by activators, enhances transcription. More common in eukaryots where it is situated some distance from the promoter.

Question 17

Architectual regulators

Answer 17

Protein that binds between promoter and activator/repressor to bend or loop the DNA so these sites are brought closer.

Question 18

Co-activators

Answer 18

Proteins that mediate interaction between RNA polymerase and the activator. This mechanism may be blocked by repressors.

Question 19

Difference between transcription state in bacteria and eukaryots

Answer 19

Bacterial transcription is on by default, and is subject to negative regulation. Transcription in eukaryots is off by default (DNA packaging) and is subject to positive regulation.

Question 20

Operon

Answer 20

A cluster of genes that are regulated together. Polycistronic mRNA in bacterie - multiple genes on the same transcript.

Question 21

Regulation of the lac-operon

Answer 21

Lac operon contains genes for beta-galactosidase (LacZ), galactose permease (LacY), thiogalactosidase transacetylase (LacA). Negatively regulated in absence of lactose. LacI has its own promoter, codes for repressor protein that binds to main operator of the Lac operon. Allolactose is an inducer for lac operon.