28.2 Regulation of Gene Expression in Bacteria

Question 1

9 examples of gene regulation in procaryots

Answer 1

Lac-operon, Trp-operon, SOS-response, Ribosomal protein, rRNA, sRNA in trans, RNA in cis, Regulation by recombination, Sigma32 for transcription of heat shock

Question 2

Operon vs Regulon

Answer 2

Operon is a set of genes regulated by the same promoter and trancribed to se same mRNA.
Regulon is a set of promoters regulated by the same regulatorprotein.

Question 3

Example of Regulon

Answer 3

Heat-shock, SOS-response, Katabolite-repression, Galactose-metabolism in yeast.

Question 4

Summary of regulation of Trp-synthesis in E. Coli

Answer 4

Transcrption of the trp-operon is negatively regulated by trp, it is a co-repressor of the trp-repressor. Trp-transcription is also regulated by attenuation dependent on trp-concentrations.

Question 5

Attenuation (and in the case of trp-operon)

Answer 5

In attenuation the transcription starts as normal, but is cut short before completion. It is coupled with translation (the speed). Trp-operon has four important sequences (1-4), binding between 2-3 allows for complete transcription, while 3-4 binding results in attenuation-structure. Concentration of trp impacts the speed of translation, higher trp means faster translation, which results in the blockage of sequence 2 and keeps it from binding to sequence 3, but allows 3-4 binding and attenuation.

Question 6

SOS-response

Answer 6

Damaged DNA gives single-strands. The RecA protein binds to these. RecA has a co-protease function which leads to the auto-cleavage and inactivation of the LexA-repressor, repressor of the SOS-genes. This leads to transcription of the whole operon and repair of DNA. Fewer single-strands means less RecA, less cleavage of LexA, and repressing of SOS-genes.

Question 7

Regulation of Synthesis of Ribosomal Protein

Question 8

Translation of mRNA by cis/trans RNAs

Answer 8

RNA can bind to trans-mRNA and affect activity or stability. Parts of mRNA in cis-configuration can regulate its own function (riboswitches).

Question 9

Riboswithces

Answer 9

Domains on mRNA that can bind ligands which changes conformation and activity of the mRNA (self-regulation).

Question 10

Regulation by Recombination

Answer 10

Phase-variation, different