BIOL SCI 215 Lecture Notes - Lecture 12: Covalent Bond, Chain Termination, Rna Interference
28 Jun 2018
School
Department
Course
Professor
5/14
Regulatory system that would act to express GAL genes using protein, GAL 4, a
transcription factor that binds to UAS sequence. This UAS lies upstream of many
genes
oUAS is a landing site
In the absence of gal, Gal80 will bind to gal4 which will bind to UAS and the rna
polymerase
Galactose activates gal 3 which has a negative effect on 80, negative effect on 4
which binds to UAS allowing for expression of Gal 1-10
is missing, there would be no expression of Gal1 and thus uninducible
UAS changed, landing site changes, leading to uninducible as well
UAS active in Cis
Dosage compensation in humans
Need an equal dose of proteins encoded on X linked genes between males and
females
In females, one X is epigenetically silenced at random in each cell leading to an
inactive X as a barr body
Model for X-chromosome inactivation
Xist transcription region
Chromatin modifying enzymes
RNA is bringing particular proteins to the particular chromosome
Xist RNA recruits chromatin modifying factors which creates heterochromatin
Inactive chromatin spreads leading to inactivating X chromosome
X-inactivation can make females phenotypically mosaic
Translational control by miRNAs and RNAi interference by siRNAs
microRNAs halt translation of specific genes by binding to 3’ UTR sequences in target
mRNAs.
Code distinct sequences
Transcribed from genome
Dicer: takes hairpin precursor and cuts off the loop so that you are left with 2 small
RNAs - 22-23 nucleotides long leading to them ending up in RISC (RNA induced
silencing complex) and it is capable of base pairing
With the help of RISC, it is able to target particular genes
RISC prevents translation
Expression of miRNA can influence expression of a gene by binding to 3’ UTR
RNA interference is a related antiviral system
microRNA pathway is related to anti-viral response
Many viruses produce double-stranded RNA
Dicer chops this into 21-23 bp RNAs called siRNAs, then they are loaded into RISC
siRNA RISC complex binds to mRNA with perfect bp then RISC makes cut in RNA
and RNA is degraded
siRNAs are small RNAs that have 21-23 nucleotides, and are designed to match particular
mRNAs, and then they will degrade them
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Regulatory system that would act to express gal genes using protein, gal 4, a transcription factor that binds to uas sequence. This uas lies upstream of many genes: uas is a landing site. In the absence of gal, gal80 will bind to gal4 which will bind to uas and the rna polymerase. Galactose activates gal 3 which has a negative effect on 80, negative effect on 4 which binds to uas allowing for expression of gal 1-10 is missing, there would be no expression of gal1 and thus uninducible. Uas changed, landing site changes, leading to uninducible as well. Need an equal dose of proteins encoded on x linked genes between males and females. In females, one x is epigenetically silenced at random in each cell leading to an inactive x as a barr body. Rna is bringing particular proteins to the particular chromosome. Xist rna recruits chromatin modifying factors which creates heterochromatin.
