Transcription (Lecture 13) Flashcards
Where is the promoter sequence located?
on dsDNA molecules
What needs to recognize dsDNA in order to begin making transcripts?
DdRp
Which DNA virus needs to bring their enzyme with them and why?
hepadnavirus and parvovirus because they have gapped dsDNA and need to repair it before transcription
Viruses need at least one protein to help them transcribe and replicate, what may be the 3 functions of these proteins
bind to DNA as a DNA-binding protein, helping with the activation of genes or work on nucleosomes and help unwind DNA
What two factors work together to help the initiation of transcription?
regulatory sequences and promoter sequences
What will enhance or silence the transcription of certain genes?
sequence-specific DNA binding proteins
What are 2 ways viruses regulate transcription? Which is more common?
autoregulatory (+ or –) or cascade; cascade is more common
What is the autoregulatory way of regulating transcription?
make a transcript »_space;> protein which comes back into nucleus and can either enhance its own transcription (+) or silence its own transcription (–)
What is the cascade regulation of transcription?
make mRNA »_space;> protein comes back into nucleus and turns on or off another gene
What are the 3 groups of genes in DNA viruses?
immediate early genes, early genes, and late genes
What are immediate early genes?
(alpha proteins) codes for transcription factors; initiates transcription and assist on turning on early genes
What are early genes?
(beta proteins) code for DNA replication proteins/enzymes; transcription factors for late genes
What are late genes?
(gamma proteins) code for capsid, assembly, and maturation
What is the benefit of having some genes made immediate early and others being made late?
not wasting time/energy on making proteins for assembly and capsid before other important proteins
What are the first genes made in dsDNA viruses?
immediate early genes
Generally, what are the 2 gene phases in DNA viruses?
early and late gene phases
What is the LT protein?
earliest early gene of SV40, antigenic protein
What are roles the LT protein carries out?
binds to Rb protein, binds to Ori and unwinds DNA, suppresses its own expression, turns on downstream proteinst
What is the early gene phase?
enzymes and regulatory proteins needed to carry out transcription and replicate genome
What is the late gene phase?
structure and assembly proteins
What are the 2 important modifications made to viral transcripts in order for host-cell ribosomes to recognize them?
5’cap and poly(A) tail
What are the 4 roles of the 5’ cap?
protect mRNA from exonucleases, efficient translation, prevent activation of antiviral responses, gets mRNA out of nucleus
What are the 2 roles of the poly(A) tail?
stabilizes mRNA and protect from degradation
