Question

Why is viral transcription temporally regulated during the infectious cycle? How is such
regulation achieved? (in your answer include positive and negative autoregulation and
transcriptional cascades).

Answer 1

life cycle of a virus after infecting a host includes several stages: Attachment, penetration, uncoating, targeting, gene expression including (transcription and translation), genome replication, assembly and maturation and release of the newly formed infectious viruses.

Among these steps viral transcription is the first biosynthetic reaction occuring in the host cells. The first step in viral transcription involve the conversion of viral genome to template.

transcription regulating proteins are classified as

1. viral / host sequence specific DNA binding proteins.

2. Molecules that co-activate viruses, modulate transcripton are required

3.several co-activators modulating the structures of nucleosomal template.

transcription is stimulated by Ad E1A proteins

Gene X Cellular components Cellular components +viral protein X Viral mRNA Protein X

above figure shows positive versus negative regulation of viral DNA

cascade regulation:

ABOVE FIGURES shows adenovirus transcriptional regulation:

1.phase transition is governed by 3 viral proteins and DNA sunthesis.

2.For E transcription unitsE1 A is required

3. DNA synthesis and L phase entry invoves E2, which increases initiation from major late promoter.

4. Lgene transcription requires IVa2.