eukaryotes- transcription factors and steroid hormones

lecture 6

what are diseases in eukaryotes?

• cancers

• autoimmune disorders

• metabolic conditions

what are transcription factors?

are proteins that bind to specific DNA sequences and regulate/ control transcription

what is basal transcription machinery?

attaches to promoter and helps Rna polymerase to attach

unwinds the DNA to initiate transcription

transcription factors that alter the rate of transcription?

turn transcription up/ down or on/ off in response to biological or environmental factors

describe the basal transcriptional complex?

• the basal transcriptional machinery

• the transcription proceeds at an exceedingly low rate

• enhanced by transcription factors

what are key characteristics of transcription factors?

what are promoters and enhancers?

Promoter

Upstream of the coding sequence of the gene

Specific motif; NOT transcribed

TATA box with consensus 5’-TATAAA-3’

Basal transcription factors bind to the TATA box, recruiting RNA polymerase

Enhancer Region

Short section of DNA found up to 1,000,000 bp up- or down-stream of the gene

Binds to transcription factors, altering rate of transcription

Different enhancers are specific to different transcription factors

What else?

Inducible

Not all genes have response elements for all transcription.

Account for different appearance and function of cells.

Silencers and repressor transcription factors

regulation through diagram…

what is combinatorial regulation?

Many genes are controlled by several different transcription factors, with a specific combination needed to turn the gene on

what class are steroid hormones?

class of lipophilic molecules derived from cholesterol

steroid hormones easily pass through the cell membrane and to?

specific receptors inside the cell

what three categories are steroid hormones divided into based on function?

Sex steroids (e.g., oestrogen, testosterone)

Glucocorticoids (e.g., cortisol)

Mineralocorticoids (e.g., aldosterone)

what type of receptors to steroid hormones bind to?

intracellular receptors

diagram of how steroid hormones work…

how are steroid hormones different from other hormones?

• not stored in vesicles

• Production can be stepped up rapidly, but still takes time

  • Ligands for transcription factors (SHR)

  • Alter gene expression

  • Therefore, response measured in hours to days

  

describe osmolarity in hormones (e.g. aldosterone)?

• Osmolarity: amount of solute per unit volume

• Drives water movement if it can!

• is important in the kidney

• Sodium

• Control sodium movement...

• ...water movement will follow

what does aldosterone do to the body?

That last sodium transporter is aldosterone-sensitive

Acts on the kidney to enhance Na⁺ retention

Therefore enhances water retention

Increases blood volume (and pressure)

Increases pressure driving formation of tissue fluid

Renin-angiotensin-aldosterone system

describe gene target for aldosterone?

Two-step process:

First is passive (Na conc in the lumen is very high)

Facilitated by ENaC

Second is active

Driven by Na⁺/K⁺-ATPase

• Both are gene targets of aldosterone

• Response elements present in the promoter

describe transcription in oestrogen and testosterone?

Key in reproductive health

Hormone replacement therapy (HRT)

Synthetic versions of these hormones

Post – menopausal symptoms or hormone deficiencies