Lecture

Introduction to Molecular and Cell Biology, Biol. 220

Lecture 20: Transcription Regulation

Inducers and repressors are molecules that bind protein regulators and modify their actions of positive and negative regulation.

An inducer is a molecule, that when bound to a protein regulator, results in transcription.
A repressor is a molecule, that when bound to a protein regulator, prevents transcription.

Prokaryotic example
Lactose operon revisited (Fig. 10.16).

Fig. 10.16

Eukaryotic mechanisms
Hormone activation (Fig. 10.67).

Fig. 10.67

Signal response systems (Fig. 10.68).

Fig. 10.68

Where are response elements located relative to promoters?

Activators that stimulate the Highly Cooperative assembly of initiation complexes.
Promoter-proximal sites (Fig. 10.60).

Fig. 10.60

Model of enhancesome that forms on the beta-interferon enhancer (Fig. 10.48).

Fig. 10.48

Distant enhancer sites (Fig. 10.61).

Fig. 10.61

Silencing of genes near telomeres
Yeast mating-type control (Fig. 10.55).

Fig. 10.55

Can you recall a mechanism that would explain HOW this exchange is done?

Fig. 12.31 Double-strand break model of meiotic recombination in the yeast S. cerevisiae.

How are the telomeric copies kept silent?

Model of silencing mechanism at yeast telomeres (Fig 10.57).

Fig. 10.57

Regulation of transcription at the chromatin level.

Repressors and activators modify the acetylation of histone tails (Fig. 10.58).

Fig. 10.58