b11 final Flashcards
what is polycistronic mRNA?
mRNA with one promoter for many genes
what is monocistronic mRNA?
mRNA with one promoter for one gene
what increases the RNA pol’s affinity for promoter sequences?
sigma factor
what does the RNA polymerase holoenzyme consist of?
RNA polymerase (5 subunits) + sigma factor
What are the two types of transcription termination sequences in prokaryotes?
- stem-loop hairpins (RNA) : intrinsic causes RNA polymerase to pause
- rho factor (protein): protein mediated, there is a binding sequence for the protein (ex. the protein is the rho factor)
what allows 1 gene to be used for production of multiple different sequences of proteins (splice isoforms) ?
Alternative splicing
what is a primary transcript/pre-RNA/precursor-mRNA?
initial RNA molecule synthesized from the template DNA
what are splicing isoforms?
different versions of mRNA that result from alternative splicing (so we have one mRNA transcript and we can cut it into different parts and this produces many parts from one single gene)
which RNA polymerase makes all eukaryotic pre- mRNA?
RNA pol II
what is the equivalent of the prokaryotic sigma factor in eukaryotes?
general transcription factors (GTFs)
what is assembled at the TATA box?
preinitiaiton complex (PIC) that contains general transcription factors (GTFs) and RNA polymerase
which general transcription factor uses ATP hydrolysis to open the DNA double helix at the transcription start point, to expose single-stranded template?
TFIIH (kinase and helicase)
*remember H form helicase
what are the roles of the general transcription factor TFIIH? (there are 2)
- uses ATP hydrolysis to open the DNA double helix aka exposes single-stranded template
- phosphorylates RNA polymerase II tail (C-terminal domain, CTD) aka signals that RNA Pol II can being elongation
what is the name for RNA sequences that do not encode protein but play important regulatory roles?
Untranslated regions:
1. 5’ UTR: methylated guanosine cap
2. 3’ UTR: Poly(A) tail
what are the three types of processing that need to occur in eukaryotic pre-mRNA?
- 5’ cap
- splicing/alternative splicing
- 3’ poly(A) tail
what is the function of the 5’ cap?
- prevents digestion by exonucleases
- plays a role in transport of nucleus
- plays a role in initiation of mRNA translation to protein
- indicator that mRNA is completed
What is polyadenylation?
addition of a string of A (adenine) nucleotides at the 3’ end of the mRNA
how many origins of replication (ori) do bacterial chromosomes have?
1
points where a pair of replicating segments come together are called what?
replication forks
A transcription factor that is activated in response to DNA damage and can prevent cell cycle progression and/or promote apoptosis
p53
Transmembrane protein that is activated by dimerization upon growth factor binding
EGFR
A transcription factor that can activate genes involved in progression from G1 phase to S phase in the cell cycle
E2F
A non-receptor tyrosine kinase that was originally discovered as a viral oncogene
Src
Many signaling pathways converge to regulate phosphorylation of this protein, which controls the R point
Rb
Form complexes with Cdks to promote/regulate events of the cell cycle
cyclins
polypeptides are linear sequences of what?
amino acids
amino acids are linked together by what kind of bond?
peptide bonds
amino acids are joined by the ______ end of one amino acid and the ______ end of another
carboxyl, amino
the amino terminus of an animo acid is also called
N-terminus
the carboxyl terminus of an amino acid is also called
C-terminus
what promotes protein folding?
non-covalent interaction (no sharing of electrons but rather opposite charges are attracted to each other)
what are the structural units of proteins called?
protein DOMAINS
can 1 polypeptide contain more than one domain?
yes
the ribosome moves what direction along the mRNA?
5’ to 3’
what are Shine-Dalgarno sequences?
- a sequence of nucleotides in bacterial (prokaryotic) mRNA that is located upstream from the AUG codon, helps align the ribosome so translation can begin
In prokaryotes, which subunit are initiation factors attached to?
small subunit of ribosome
in prokaryotic translation what do initiation factors do? (3)
- Attachment to mRNA
- Attachment of first AA-tRNA
- Preventing premature attachment of large subunit
what is a kozak sequence
A Kozak sequence is a specific nucleotide sequence found in eukaryotic mRNA that is important for the initiation of translation. It helps the ribosome recognize the start codon where translation begins.
what is a polyribosome or polysome?
multiple ribosomes associated with an mRNA
What happens to the CTD of RNA polymerase to cause proteins involved in capping, splicing, and cleavage/polyadenylation to bind to it?
it is phosphorylated
Helps loosen DNA/histone interactions to transcribe through nucleosomes
transcription elongation factors (Spt4, Spt5, and Elf1)
which is usually longer: introns or exons?
introns
what Initiates transcription elongation by phosphorylating RNA polymerase II
TFIIH
what Binds to the TATA Box
TFIID (with TBP)
Unwinds DNA at the site where transcription will begin
TFIIH
Coordinates recruitment of different processing enzymes in close proximity to the growing strand of new RNA
CTD
Creates a 5’-5’ triphosphate bridge to a GMP at the 5’ end of the RNA
capping enzyme, Guanyl transferase
Adds a string of adenine nucleotides to create the poly(A) tail
poly(A) polymerase