BSCI330 regulation of mRNA levels Flashcards
where is the first place gene expression regulation can occur
mRNA level - can be regulated a transcriptional initiation, elongation, splicing, nuclear export, degradation
what is primary regulation
matching RNA synthesis to expression requirements avoids the expense of synthesizing unneeded macromolecules
what are transcription factors
gene regulatory proteins - sequence-specific DNA-binding proteins
what are the major and minor grrove
represent the opposite faces of a base pair
each base on a strand can be distinguished in the major groove
only AT base-pairs and GC base-pairs can be distinguished in the minor groove
what is the helix-turn-helix binding motif
two alpha helices connected by a short unstructured stretch
C-terminal recognition helix makes sequence-specific contacts in the major groove of DNA
generally bind to DNA as symmetric dimers, where recognition helices bind to half-sites separated by one turn of the DNA helix
what is the homeodomain
a special case of helix-turn-helix motif
a larger structure that includes a helix-turn-helix region plus other highly conserved structures
conserved structure suggests that all homeodomains are presented to DNA in the same fashion
what are zinc fingers
one or more zinc ions is coordinated by amino acid side groups
one subclass uses 2 cysteines and 2 histidines to coordinate zinc between an alpha helix and a 2-strand antiparallel beta sheet
second subclass coordinates 2 zinc ions, using 4 cysteines for each
one zinc ion stabilizes a recognition helix and one stabilizes a loop involved in dimerization
what is the leucine zipper
alpha helix containing a hydrophobic surface on one side
protein binds DNA as a dimeric structure
the helix from one subunit binds to the corresponding helix in the second subunit in a coiled-coil structure - hydrophobic interactions
what is helix-loop-helix
a short alpha helix is connected to a longer alpha helix by a flexible loop
loop allows one helix to fold back and pack against the other
acts as both a dimerization interface and the DNA-binding region
what is heterodimerization
between two different members of the same class - increases the range of sequences that can be recognized
what does dimerization of DNA-binding proteins do
enhances binding and specificity by increasing the contact area with DNA
what is the promoter region
promoter is the region where RNA polymerase and the general transcription factors assemble
it is always a short distance upstream of the 5’ end of the gene
what is the enhancer region
an independent region outside the promoters
can be anywhere
this region cannot drive transcription on its on but increases transcription initiation from its corresponding promoter
what are the two ways transcription factors can work
cooperatively (two activators) or antagonistically (activator vs a repressor)
how are transcription factors activated
phosphorylation (converts an inactive form into an active form or vice versa)
