operons

PRO only

physical grouping of related genes

expressed under same conditions

may be inducible or repressible

lac operon

structure

type

inducer

lac1(repressor)-promoter-operator-structural genes

inducible (constitutively off), repressor gene on-->creates repressor protein, which binds operator

lactose binds repressor protein, changing conformation and preventing it from binding operator

lac operon products

when lactose is present, repressor protein inactivated, and lactose metabolism enzymes are produced:

lac permease--transports lactose into cell

beta-galactosidase: cleaves lactose into glucose and galactose, producing E

Trp Operon

type

product

mechanism

repressible (constitutively ON)

enzymes necessary for trp synthesis

trp is being produced, until tryptophan binds repressor protein, allowing it to bind to operator and turn off gene transcription

promoters

DNA seq recognized by transcription factors responsible for determining transcription start site and initiating low levels of transcription

enhancers

DNA seq responsible for enhancing transcription levels/ regulating cell- and tissue-specific transcription

recognized and bound by specialized transcription factors

response elements

DNA seq that bind transcription factors

transcription factor structure

DBD: DNA-binding domain

TAD: trans-activating domain (binding sites for transcription coregulators)

SSD (optional): signal-sensing domain, envtl factors-->up/down regulation

AFs

activation functions

binding sites for transcription coregulators on transcription factors

transcription factors

mechanism of action

stabilize or block binding of RNA polymerase to DNA

catalyze acetylation, deacetylation of histones

recruit coactivator/repressor proteins

Zinc finger proteins

transcription factors

produce loop (via zinc chelation) that binds to DNA

helix-turn-helix proteins

transcription factors

3 alpha helices, joined by curved sections of polypeptide (homeodomain)

developmentally important, not produced in post-natal life

helix-loop-helix proteins

transcription factors

need to dimerize to bind to DNA

leucine zipper proteins

transcription factors

dimerize by means of leucine zipper: alpha helix containing a critical Lys

steroid receptors

transcription factors

contain steroid-binding domain, bind steroids which regulate activity

transcription factors are activated by:

envtl signals (stress signals): e.g. heat shock genes

hormones and growth factors

Rett syndrome

neurodevelopmental disorder

mutation in MECP2 transcription factor

diabetes, MODY

Maturity onset diabetes of the young

mutations in hepatocyte nuclear factors or insulin promoter factor 1(HNFs or IPF1/Pdx1)

developmental verbal dyspraxia

mutations in FOXP2 transcription factor

developmental, can't speak

IPEX (autoimmune disease

FOXP3 transcription factor mutation

Li-Fraumeni syndrome

p53 transcription factor mutation-->cancers

STAT family

 transcription factors

breast cancer

HOX family

transcription factor

cancers

mRNA and protein regulation

mRNA processing, half-life, and translation can be regulated to modify protein expression

processing determines translation, since mRNA will not be transported out of nucleus for translation until processing

introns/exons in higher eukaryotes

higher eukaryotes have larger percentage of genes containing introns, and introns are larger

regulation of mRNA half-life

info found in 3'UTR: AUUUA is signal for early degradation (more times sequence is present, shorter lifespan)

poly-A binding protein

removal-->poly A tail degradation, destabilization of mRNA-ribosome complex