Transcription Factors

Question 1

What are the main structural motifs for classifying TFs into families?

Answer 1

DNA binding domains or dimerisation domains.

Question 2

What is the effect of CBP?

Answer 2

HAT activity and recruits RNA pol II.

Question 3

What ways can factors interact?

Answer 3

DIMERISATION (of bHLH, bZIP and nuclear factors)

Binding of CO-FACTORS (CBP to phosphorylated CREB) or co-repressors (THR)

Question 4

Give an example of factor competition.

Answer 4

Drosophila even skipped promoter

Overlapping binding sites for transcriptional activators & repressors.

Eve expression dependent on relative []s of factors in different parts of promoters.

Question 5

Describe the GH promoter.

Answer 5

2 bindings use for Pit-1 (AP specific Tf)
2 binding sites for glucocorticoid R
2 binding sites for CREB

Question 6

What are the three subtypes of HTH’s?

Give examples of homeodomain proteins.

Answer 6

Homeodomain, POU, PAX factors.

HOM-C genes in drosophila
HOX genes (humans)
Mutation in HOXD13 –> finger fusion

Question 7

What are the PAX genes?

Answer 7

Regulate cell fate during embryonic development.

Pax-6 - eye development (human anridia mutation)

Pax-3 (Waardenburg syndrome type 1 - abnormal pigmentation - nc development affected).

Question 8

What are Fos/Jun

Answer 8

LZ tfs
AP-1 assembled by dimerisation of bZIP of Jun and Fos

AP1 recognition sequence bound 30x more strongly by heterodimer.

Question 9

What is a pioneer TF?

Answer 9

Certain Tfs bind targets in condensed chromatic independently - opens chromatin enabling other factor binding.