Gene Regulation

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Processes regulated at genetics level

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metabolism, response to environmental stress, cell division

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Constituitive

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always expressed, continuously needed for organism to survive

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Most common way to regulate a gene

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control rate of transcription

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Regulatory proteins

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repressor and activator

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repressor

Back 5

bind to RNA polymerase, inhibits transcription negative control

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activator

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binds to DNA and increase transcription, positive control

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Small effector molecules

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inducer and corepressor

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inducer

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effector molecule that increases transcription by binding to repressor to prevent it from binding to DNA,

binds to activator to make it bind to DNA

Front 9

Regulatory proteins bind to

Back 9

DNA

Front 10

Small effector molecules

Back 10

bind to regulatory proteins

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corepressor

Back 11

effector molecule that reduces transcription by binding to repressor to cause it to bind to DNA

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inhibitor

Back 12

binds to activator to prevent it from binding to DNA

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repressor + inducer

Back 13

Inducer binds to repressor, repressor cant bind to DNA, TRANSCRIPTION OCCURS

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repressor + corepressor

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corepressor binds to repressor to help it bind to DNA, TRANSCRIPTION DOES NOT OCCUR

Front 15

inducer + activator

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inducer binds to activator to help it bind to DNA, TRANSCRIPTION OCCURS

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activator + inhibitor

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inhibitor binds to activator so it cannot bind to DNA, TRANSCRIPTION DOES NOT OCCUR

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enzyme adaptation

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cell only produces enzymes when a substance needs to be metabolized by that enzyme

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operon

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group of 2 or more genes under transcriptional control by a single promoter

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promoter

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signals beginning of transcription

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terminator

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signals end of transcription

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polycistronbic mRNA

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RNA that contains sequences of 2 or more genes with common functional goal

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lacZ

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encodes b-galactosidase, converts lactose to galactose and glucose, and also lactose to allolactose

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lacY

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encodes lactose permease, actively transcports lactose into cytoplasm

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lacA

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encodes galactosidase acetyltransferease and covalently modifies lactose

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CAP site

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catabolite activator protein site, DNA sequence recognized by CAP

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operator

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sequence of bases that provides binding site for repressor

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lacI

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encodes lac repressor and regulates operon binding

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lac I (negative)

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constituitive even when inducer is absent

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lac I (S)

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super-repressor, repressed even when inducer is present

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allosteric regulation

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small effector regulates transcription

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merozygote

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carries F' factor, partially diploid, may be different alleles

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trans-effect

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for of gene regulation of 2 DNA segments that are not adjacent to each other

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trans-acting factor

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repressor

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cis-acting element

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operator

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catobolite

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substance broken down inside the cell

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catobilite of lac operon

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glucose

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diauxic growth

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sequential use of 2 sugars

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effector of lac operon

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cAMP

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relationship between cAMP and glucose

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When glucose is present, cAMP levels are low and cannot bind to CAP protein for CAP to bind to CAP site and increase transcription

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pseudo-operator

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if either of the pseudo-operators are missing, transcription will be repressed

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attenuation

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transcription begins but is stopped before most of trp operon is transcribed

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attenuation termination occurs...

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right after TrpL gene

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TrpL

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gene that encodes for 15 AA that for trp leader peptide

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intrinsic termination loop

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3-4

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when tryptophan levels are low

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ribosome shields 1 region so 2-3 loop forms and 3-4 loop cant form

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when tryptophan levels are high

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ribosome does not shield region, so 1-2 loop forms then 3-4 loop forms and transcription is terminated

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TrpR

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has its own promoter, not a part of trp operon, encodes for trp repressor protein

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corepressor of trp operon

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tryptophan

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Catabolic operon are often

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inducible

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anabolic operons are often

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repressible

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posttranlational regulation

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functional control of proteins already present

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translational repressors

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bind to mRNA to inhibit translation by binding to Shine-Dalgarno sequence so rRNA cant bind to initiate translation

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Antisense RNA

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RNA strand that is complementary to mRNA strand

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Example of antisense RNA in E. coli

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ompF protein is produced by ompF gene if water concentration is low, if water concentration is high, micF inhibits the ompF gene so ompF protein is not produced

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ompF gene

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gene in bacteria that is important for osmoregulation and water concentration`

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allosteric enzyme

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enzyme that contains 2 sites, 1 catalytic site to bind and convert substrate, 1 regulation site, if something is bound then conversion site wont work

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anti-terminator loop

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riboswitch to regulate transcription when TTP levels are low

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terminator loop

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riboswitch to turn off transcription when TTP levels are high

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Shine-Dalgarno sequestor

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makes ribosome binding not accessible so translation cannot occur

Front 60

Shine-Dalgarno antisequestor

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makes ribosome binding site accessible so translation can occur