• respond to changes in nutrient availability
• respond to enviromental stresses

• expression of genes in an accurate pattern during the arious developmental stages in the life cycle
• differences among distinct cell types

proteins that influence the ability of RNA polymerase to transcribe a given gene

have two main types

• required for the binding of RNA pol to the core promoter and its progression to the elongation stage
• necessary for basal transcription

• serve to regulate the rate of transcription of target genes
• influence ability of RNA pol to begin transcription of particular genes

eukaryotic genes are regulated by many factors

• 1+ activator proteins stimulating transcription
• 1+repressors inhibiting transcription
• activators/repressors being modified (binding small effector molecules, protein-protein interactions, covalent modification)
• regulatory proteins alter nucleosome near promoter
• DNA methylation may inhibit transcription
  

have specific funcitons

• one domain could be for DNA-binding
• another provides a binding site for effector molecules

• bidirectional (function forward or reverse)
• usually located within a few hundred nucleotides upstream of promoter

1. binding of small effector molecule, such as a hormone
2. protein-protein interactions
3. covalent modification such as phosporylation

regultory transcription factors that respond to steroid hormones

(hormone binds to transcription factor)

affect gene transcription

• produced by endocrine gland
• secreate into bloodstream
• taken up by cells responding to the hormone

• Glucocorticoids (influence nutrient metabolism)(promote glucose utilization, fat mobilization and protein breakdown)
• Gonadocorticoids (estrogen and testosterone) (influence growth and funciton of gnads)

• closed (chromatin tightly packed)(transcription difficult/impossible)
• open (chromatin acessible to transcription factors)

1. acetylation
2. methylation
3. phosphorylation

a change in chromatine structure that silances gene expression (carried out by enzyme DNA methyltransferase)

common in some eukaryotes

yes

may explain genomic imprinting

(specific genes in gametes are methylated)

pre-mRNA can be spliced in more than one way

produces more than one polypeptide with different amino acid sequences

large sections of teh coding region are the same, resulting in alternative versions of a protein that ahve similar functions resulting in enough difference in amino acid sequences to provide each polypeptide with its own unique characteristic

•  varies considerably (minutes or days)
• can be regulated so that its half-life is shortened or lengthned (influencing mRNA concentration/consequently gene expression)
• effected by factors such as
  

1. length of polyA tail
2. Destabilizing elements
   

micro RNAs

(miRNAs)

and short-interfering RNAs (siRNAs) cause RNA interference where genes do not encode a protein and gives rise to small RNA molecules.

They are encoded by genes

• presents a newly identified form of gene regulation
• may offer a defensive mechanism agains certain viruses (RNA double-stranded RNA viruses)
  
• may play a role in silencing certain transposable elements (random insertion may place an element near a cellular promoter which will produce a silencing RNA)