28.3 Regulation of Gene Expression in Eukaryotes

Question 1

Regulatory Sequences

Answer 1

TATA box as promoter for polymerase. Enhancers or upstream activator sequences as regulatory sequences that increase transcription.

Question 2

Requirements for Binding of Polymerase to Promoter

Answer 2

Transcription activators that bind to enhancers, Architectual regulators that facilitate DNA looping, Chromatine modification and remodeling proteins, Co-activators, and Basal transcription factors.

Question 3

Combinatorial Control

Answer 3

Most genes are regulated by a combination of transcription factors, variants of proteins of the same family can combine to different transcription factors.

Question 4

Steroid Hormone for Gene Regulation

Answer 4

Steroids diffuse through membrane and binds to receptor, hormone-receptor complex binds to DNA sequences called Hormone Response Elements (HRE). The receptor act as activators and recruits coactivators and polymerase to transcribe the gene(s).

Question 5

lncRNAs as Regulatory Elements (example)

Answer 5

lncRNAs are regulatory elements of hormone receptors. For example the GAS5 inhibits transcription activation through glucocorticoid receptors by competing with DNA for receptor binding.

Question 6

Phosphorylation of Transcription Factors

Answer 6

Non-steroid hormones that bind to membrane receptors can cause a cascade that results in phosphorylation of regulatory proteins that affect the transcriptional activity. For example the activity of beta-adrenergic receptors (G protein coupled receptors), cAMP-depentent protein kinase (PKA) etc (Chapter 12).

Question 7

cAMP response response element (-binding protein) (CRE(B))

Answer 7

CRE are DNA sequences that are activated by CREBs working as transcription factors. The catalytic part of PKA may move into the nucelus and activate CREB.