Chapter 8 - Transcription and RNA Processing Study Guide

A series of flashcards summarizing key concepts from Chapter 8 regarding Transcription and RNA Processing in the context of viral infections.

What is the first biosynthetic event after viral DNA enters the nucleus?

Transcription of immediate-early genes by host RNA polymerase II.

Why is transcription of immediate-early genes the first event after viral DNA enters the cell?

The virus needs regulatory proteins and replication factors before DNA replication.

Where does the transcription of viral immediate-early genes occur?

In the nucleus.

What are the steps in viral mRNA production and processing?

1. Initiation: RNAP II binds to the promoter; 2. Capping (5' cap); 3. Elongation and splicing; 4. Polyadenylation (3' poly(A) tail); 5. Export through nuclear pores.

How is RNA polymerase II (RNAP II) recruited to the DNA template?

Viral proteins hijack host transcription activators to recruit RNAP II to viral promoters.

How do repressors affect host transcription?

Repressors block host transcription.

What methods are used for transcription regulation in viruses?

Regulation is achieved through enhancers, promoters, viral transcription factors, and phosphorylation of RNAP II CTD.

What is the purpose of splicing?

To expand coding capacity of small viral genomes.

Provide an example of splicing in viral genomes.

Adenovirus uses alternative splicing to express over 20 proteins from limited genes.

What proteins do viruses encode to export unspliced viral mRNAs?

Proteins that bypass host quality control.

What is an example of a viral protein that helps export unspliced viral mRNAs?

HIV Rev protein binds to Rev-response elements to export unspliced genomic RNA.

What are the phases of temporal regulation of viral transcription?

1. Immediate-early genes regulatory proteins; 2. Early genes encoding DNA replication machinery; 3. Late genes encoding structural proteins.

How does positive autoregulation work in viral transcription?

Viral proteins activate the next phase of transcription.

What is negative autoregulation in viral transcription?

It shuts down the previous phase of transcription.

How do transcriptional cascades control infection timing?

They ensure that different phases of transcription occur at the correct time throughout the infection cycle.

What is the role of 5' capping in mRNA processing?

It protects mRNA from degradation and helps in ribosome binding for translation.

What does polyadenylation refer to in mRNA processing?

The addition of a poly(A) tail at the 3' end of the mRNA for stability and export.

What is the significance of initiating transcription in the nucleus?

It is where the DNA template is located and where mRNA processing begins.

Why are early genes important in the viral life cycle?

They encode the DNA replication machinery necessary for viral replication.

What do late genes typically encode in viruses?

Structural proteins that form the viral particle.

How do enhancers contribute to transcriptional regulation?

They increase the likelihood of transcription by enhancing the recruitment of the transcription machinery.

What is the impact of host transcription repressors on viral gene expression?

They inhibit the expression of host genes, allowing for viral genes to be expressed instead.

Why is the splicing process important for small viral genomes?

It allows a limited number of genes to produce several proteins through alternative splicing.

How can viruses evade host immune responses during transcription?

By using viral proteins to modulate the immune recognition of infected cells.

What role do transcription factors play in viral transcription?

They facilitate the recruitment of RNA polymerase and regulate the transcription process.

What would happen to unspliced mRNAs without viral proteins like Rev?

They would be subject to host quality control and likely degraded instead of exported.

Why are immediate-early genes crucial in the context of viral infections?

They provide the necessary proteins for coordinating the viral replication cycle.

How does splicing affect nuclear export of mRNAs?

Splicing marks cellular mRNAs for export while unspliced ones are retained.