finals - DNA binding proteins Flashcards
_____ Gene regulatory proteins that recognize and bind to specific DNA sequences and either promote or inhibit gene transcription by RNA pol
DNA-Binding Proteins
____ the two domains of DNA binding proteins
DNA binding domain and Transcription activation (inhibition) domains
(T/F) Surface of proteins are exactly complementary to surface topography of recognized DNA sequence
true
which of the ff is not an interaction made between DNA binding proteins and DNA?
a. ionic bonds
b. covalent bonds
c. hydrogen bonds
d. hydrophobic interactions
B
(T/F) each of the protein- DNA binding is strong
false
Each protein-DNA interaction is weak but typical DNA-binding protein subunit forms about 20 contacts with DNA to generate tight interaction
___ The protein motifs that mediate DNA-binding on the major groove
αhelices or βpleated sheets
which of the ff is not a major DNA-binding motif?
a. Helix-turn-helix (HTH)
b. Carboxy-terminal portion
c. Zinc fingers
d. Leucine zipper
B
this is part of HTH
which of the ff does not apply to helix-turn-helix?
a. 2 αhelices is connected by lysine in its β turn region
b. Each α helical region spans about 8 amino acids separated by 3.4 amino acid β turn
c. The amino acids of HTH motifs tend to be highly conserved among different HTH proteins
d. Found in hundreds of DNA-binding proteins in prokaryotes and eukaryotes
A
glycine is in the turn coz its small
_____ the HTH recognition helix that regulates
sequence-specific binding of protein to DNA and fits into the major groove
Carboxy-terminal portion
______ helps align or position recognition HTH along DNA
N-terminal helix
*(T/F) HTH proteins are typically polymers
false
are dimers
(T/F) regions of proteins outside HTH motif can vary considerably in structure (sequence) among different proteins and each may also contact the DNA to modulate the interaction
true
(T/F) binding region on DNA for each recognition helix of each member of the dimer is separated by exactly two turn of DNA helix
false
by one turn only! one turn = 3.4nm
which of the ff does not apply to the DNA binding by dimeric proteins?
a. recognition helices of the dimer bind symmetrically to symmetrical DNA sequences
b. each monomer forms nearly identical contacts with the DNA region
c. symmetrical interactions significantly increases the binding affinity of the proteins for the DNA
d. none of the above
D. all applies :)
(T/F) zinc finger motifs and HTHs contain amino acids plus zinc ions
false
this only applies to Zn finger motifs
which of the ff does not apply to Zn finger motifs?
a. exists as a monomer
b. can exist in clusters of direct repeats
c. Zinc ions coordinate two cysteine and two histidine residues at base of a 12 amino acid loop
d. zinc holds together an α helix and a β sheet (secondary structure)
A
either in clusters (multiple fingers) or dimeric
_____ example of molecules that have multiple Zn finger repeats
Transcription factor for RNA pol lll, TFlllA,
which of the ff does not apply to multiple zinc finger proteins?
a. Zinc fingers follow one another along the major groove
b. Multiple repeats mediates strong and specific binding to DNA
c. Number of zinc finger repeats are similar among different proteins
d. Provides a mechanism for cells to regulate the strength of DNA binding
among different transcription factors
C
it VARIES among diff proteins
*(T/F) Arginine and histidine residues in multiple Zince fingers form hydrogen bonds with guanine bases
true
(T/F) β-pleated sheet regions of zinc fingers mediate binding to major groove of the DNA
false
this is done by alpha helices
(T/F) zinc finger repeats varies among different proteins but zinc fingers have similar amino acid sequences and contact DNA bases in similar ways
true
*_____ the aa that is commonly iinvolved in the DNA-multiple zinc protein binding Interactions
arginine
*(T/F) DNA-protein interaction occurs between arginine of a DNA-binding protein and guanine in DNA which has a specific arrangement of hydrogen-bond acceptors that is
unambiguously recognized by the side chain of arginine in the major groove
true
(T/F) Dimeric zinc finger proteins are mostly of extracellular receptors
false
intracellular
(T/F) Each monomer forms a structure similar to that of HTH motif except it has two α helices that are held together by a zinc ion
true
which of the ff is not true about dimeric zinc proteins?
a. both α helices interacts with major groove
b. structure is similar to HTH proteins
c. are intracellular receptors
d. its helices are held together by zinc ions
A
only ONE of the two helices interact w/ major groove
____ is the third major type of DNA binding motif
Basic Region-Leucine Zipper Motif
BRLZM
which of the ff is not true about BRLZ motif?
a. has arginine
b. leucine residues every 6th position
c. has histidine
d. has lysine
B
leucine residues every seventh position
______ the basic aa that BRZL motif contains
Lys, arg, his
___ # of aa every one turn of α helix
3.6 aa
(T/F) all lysine residues in BRLZ motif line up on one side of α helix
false
all LEUCINE
which of the ff is not true about BRLZ motif?
a. can be homo or heterodimeric
b. leucine residues mediate hydrophobic interactions between monomers
c. leucines hold monomers together at one end
d. one side interacts with phosphate groups in the major groove
all is true
(T/F) Basic residues at other end form electrostatic interactions with the
phosphate groups of the DNA backbone and permit interactions between the side chains of amino acids with the major groove
true
(T/F) Some transcription factors also use β sheet structure to recognize information on the surface of the major groove
true
_____ Regulates genes encoding enzymes involved in methionine synthesis in bacteria by binding to dimeric repressor and alters its conformation so that it can associate with DNA and shut off genes involved in met synthesis
met repressor
which of the ff is not true about mRNA processing in eukaryotes vs prokaryotes?
a. both mRNA are spliced to remove introns from exons
b. only euk mRNA have 5’ cap and 3’ polyadenylation
c. prok mRNA is polycistronic
d. euk have the ability to synthesize several proteins from same gene
A
splicing is only in eukaryotes
no introns in prokaryotes
(T/F) both eukaryotes and prokaryotes have mRNA transcripts that are covalently modified at both ends that allows cell to determine whether both ends of mRNA are intact for export out of nucleus and into cytoplasm
false
this only applies to eukaryotes.
mRNA end in prokaryotes not modified
(T/F) in eukaryotic mRNA, 5’ end modified by addition of a 7’-methylguanosine cap while the 3’ end is modified by addition of a poly A tail
true
____ the process where eukaryotes can produce multiple proteins from same gene
alternative splicing
(T/F) the C- terminal
domain of RNA pol ll must be first phosphorylated before it can shed most of the general transcription factors and begin transcription of mRNA
true
which of the ff is not true about the mRNA pol II in humans?
a. has aa repeats that contain two serine residues that can be phosphorylated
b. a total of 104 negatively charged phosphate
groups can be produced
c. phosphorylation both dissociates proteins of the initiation complex and allows a new set of proteins to bind
d. Enzymes jump from nascent RNA transcript to tail of enzyme
D
from enzyme tail to RNA = transcribes and processes the new RNA transcript at same time
(T/F) 5’ end of RNA transcript is modified by addition of a modified guanine nucleotide after about 25 ribonucleotides have been added
true
(T/F) the final mature cap consists of a guanylate (GMP) residue that is methylated at the N7
position and bound to the adjacent residue by a reverse 5’-5’ triphosphate linkage
true
not the regular 5’ to 3’ phosphodiester linkage
____ the methylated regions in eukaryotic mRNA
the 2’-hydroxyl group of first 2 ribonucleotides
_____ the term for the methylated ribonucleotides and presence of the
7-methylguanosine cap in eukaryotic mRNA
2’-O-methylribosyl groups
which of the ff is not a function of 7-Methylguanosine mRNA cap?
a. marks 3’ end of mRNA
b. helps to distinguish mRNA’s from other types of
RNA’s in the cell
c. protects the mRNA from degradation by exonucleases
d. functions in the processing, exporting, and translation of the mRNA in
the cytosol
A
marks 5’ end
______ a group of proteins that bind the 7-Methylguanosine mRNA cap in the nucleus
cap-binding complex (CBC)
____ are eukaryotic genes that contain both introns and exons
split genes
(T/F) both introns and exons are present in initial mRNA transcript but only exons occur in final mRNA products
true
_____ process by which introns are removed from the mRNA product
mRNA splicing
(T/F) RNA splicing applies to all types of RNA
false
primarily restricted to production of mRNA
____mRNA which has not been spliced
precursor-mRNA or pre-mRNA
(T/F) only after 5’ and 3’ processing and splicing has occurred is RNA product
referred to as mRNA
true
(T/F) both initial pre-mRNA and mature mRNA transcript contains introns and 5’ and 3’ untranslated regions
false
mature mRNA = exons only & 5’ and 3’ ends modified with a 7-methylguanosine and poly-A tail
which of the ff is not an advantage of RNA splicing?
a. facilitate the evolution of new proteins by recombination with new set of exons
b. permits a single gene to encode multiple proteins by alternative splicing of different exons
c. produce protein isoforms with varying regulatory and specialized functions
d. yield different protein encoding mRNAs (60% of genes)
C
isoforms of related but specialized functions
_____ the molecular machinery about a size of a ribosome that splices out introns, consists of complex of 5 other RNAs and over 50 proteins
spliceosome
which of the ff does not apply to mRNA spliceosome?
a. hydrolyzed ATP per splicing event
b. can recognize and manipulate only one type of intron at a time
c. ensure accuracy of splicing
d. prevent defective splicing
B
on all types of introns!
(T/F) in RNA splicing, the 2’ OH of a specific adenine in intron sequence attacks and cuts phosophodiester bond at the 5’ splice site
true
(T/F) in RNA splicing, the cut 5’ end of the intron becomes linked to the adenine to form loop structure at the “branch site”
true
(T/F) in RNA splicing, the released 5 ‘OH end of exon sequence reacts with 3’ end of adjacent exon to join the two exons and release lariat-shaped intron
true
(T/F) spliced introns are recycled
false
are degraded
(T/F) the mRNA splice sites are marked by poly-A sequences the the 3’ end of introns
false
introns have GU at 5’end and AG at 3’ end
____ the conserved sequence at the branch site at base of intron loop
PyNPyPuAPy
(T/F) Branch site typically occurs 18 to 40 bases upstream from 3’ splice site
true
(T/F) RNA splicing is performed primarily by proteins
false
by short RNA molecules (snRNAs)
which of the ff is false about the snRNAs of the spliceosome?
a. 100 to 200 nucleotides long
b. Recognize intron-exon
borders and intron branch sites through complementary base pairing
c. has high content of uridine residues
d. snRNA is complexed with at least 7 different proteins to form BBPs
D
forms snRNPS
which of the ff is not a component of the spliceosome?
a. U7 snRNA
b. snRNPS forms the core
c. U2AF protein
d. branch-point binding protein (BBP)
A
there’s no such thing :)
which of the ff does not apply to the spliceosome?
a. recognize splicing consensus sequences on premRNA
b. bring the two ends of intron together
c. catalyze splicing reactions
d. none of the above
D
all applies :)
____ a fatal autoimmune disease frequently caused by generation of
autoantibodies against proteins associated with U1 snRNP. Onset is often in late adolescence/early adulthood and causes rash on cheeks and forehead
Systemic Lupus Erythematosus
___ & ___ recognize the branch-point site of introns during the splicing reaction
BBP and U2AF protein
(T/F) during the splicing reaction, U2 snRNP displaces BBP and U2AF and the U1 snRNP binds to the 5’ splice site through complementary base pairing
true
(T/F) the splicing mechanisms and arrangements of snRNPs are independent of ATP
false
(T/F) introns and exons both tend to be uniform in size
false
introns vary, exons are uniform in size
(T/F) Binding of serine and arginine rich proteins to exons of the nascent RNA molecules regulate selection of splice sites by
spliceosomes
true
(T/F) association of spliceosome components with the RNA as it is synthesized regulate selection of splice sites by
spliceosomes
true
which of the ff does not apply to splice-site selection of spliceosome?
a. Assembly of spliceosome begins as soon as 5’ end of premRNA emerges from Pol ll
b. Spliceosome components are bound to phosphorylated N- terminal
tail of Pol ll
c. By binding 5’ splice site as it is synthesized splicing apparatus may be able to
keep track of the very next splice site (3’ end of same intron)
d. spliceosome assembly may occur during transcription but splicing occurs post transcription
B
bound to C-terminal
_____ are components of spliceosomes that assemble on exon sequences and mark off 5’ and 3’ splice sites of each intron/exon border which enhances fidelity of splicing mechanism
SR proteins (serine and arginine rich)
which of the ff is not true?
a. SR proteins mark exons
b. hnRNP proteins preferentially bind introns
c. U1 snRNP at 5’ splice site
d. U3 snRNP at 3’ splice site
D
U2 snRNP at 3’ site
____ is the complex where long introns are packaged. This facilitate the ability of splicesomes to differentiate
introns from exons and are larger than nucleosomes
heterogeneneous nuclear
ribonucleoprotein (hnRNP) complexes
___ introns that catalyze removal of their own introns without help of proteins or any other RNAs
Self- Splicing Introns
_____ RNA molecules that are capable of catalyzing their own chemical reactions
ribozymes
____ discovered the first ribozyme - The self-splicing pre-rRNA of the ciliate Tetrahymena
Thomas Cech
