Ch.8 DNA Template Flashcards
What does a DNA virus need to synthesize proteins?
Viral mRNA (via DNA dep. RNA Pol.)
What is a hallmark of DNA viruses?
expression in a strictly defined sequence
What is made during the initial period of infection?
Enzymes and regulatory proteins
What is made after viral DNA synthesis?
Structural proteins
In eukaryotes, what does RNA Pol I make?
Ribosomal RNA
In eukaryotes, what does RNA Pol II make?
mRNA species and precursors of small regulatory RNA
In eukaryotes, what does RNA Pol III make?
tRNA
When are dsDNA virus ready to be transcribed?
Once they enter the nucleus.
Initiation of transcription by Pol II is mediated by a
promoter region
What is present in the transcriptional control region?
The promoter along with a set of DNA sequences controlling transcription.
What are core promoters? What is their hallmark?
Sequences necessary for recognition and assembly of pre-initiation complexes; TA rich sequences 20-35bp upstream of the initiation site (TATA box)
What recognizes the TATA box?
TATA-box binding protein
What is a holozyme?
RNA Pol II in complex with proteins poised to initiate transcription
What are the three steps of transcription via Pol II
promoter recognition, unwinding of DNA, movement of transcriptional complex
Does a regulatory sequence have to be local?
NO, local and distant sequences can control transcription
What recognizes local regulatory sequences?
Sequence specific DNA binding proteins (first seen in SV40)
What are enhancers? How far can they be from the start site?
DNA elements that can stimulate transcription. THey can be up to 10000 bp away
What are the common properties of transcription regulating proteins?
They have a DNA binding domain; They dimerize to bind to DNA through dimerization domain; Activation domain function as an independent unit; Coactivator binding sites (modulate transcription by modification of transcription regulating proteins)
what are the two patterns of viral regulation of RNA pol II?
1-positive autoregulatory loop: rate of transcription is stimulated but doesn’t change what is being produced;
2-transcriptional cascade: Viral transcriptional units are activated in a fixed sequence.
What are the 3 categories of DNA viral genes?
immediate early; early; late. IE and E are transcribed to ensure genome replication occurs before L proteins are produced. L are generally structural proteins
The Adenovirus genome contains____ RNA pol II transcriptional units which encode more than ___ proteins
8; 40
In adenovirus what is required for progression of the infectious cycle? why is it required?
Functional E1A; it is necessary for transcription of early genes, E2, which is necessary for viralDNA syn. and entry into late phase
Unlike adenovirus, HSV1 imporants structural protein _____ during infection. What is it necessary for? How does it work?
VP16; efficient transcription of IE genes; it lacks a DNA binding site but it has an acidic activation domain which stimulates unwinding of DNA by another protein.
Epstein-Barr virus expresses ____ after infection. what regulator interrupts latency? What represses this protein?
only a few genes required for replication (latent phase) ; Zta (a sequence specific binding protein); binding with cellular proteins p53 and p65
Drugs or mutations that inhibit replication also inhibit _____ ___ _______ ________
synthesis of late genes
What is the latency/lytic state regulated by?
transcriptional programs
