1. Uncoating and nuclear import: Upon entering the host cell, the adenovirus particle undergoes uncoating, shedding its outer protein coat. The partially uncoated virus, known as the core particle, is then transported into the nucleus via nuclear pore complexes.
2. Chromatin decondensation: The viral DNA within the core particle is tightly packaged in a condensed chromatin structure, similar to the host cell's chromatin. This condensed chromatin restricts transcription and gene expression. To overcome this, the virus employs viral proteins, such as the adenovirus DNA-binding protein (DBP), that bind to the viral DNA and induce chromatin decondensation.
3. Recruitment of host factors: Adenoviruses manipulate host cell factors to remodel the viral chromatin. These host factors include chromatin remodeling complexes, histone modifying enzymes, and transcription factors. The viral E1A protein plays a crucial role in recruiting these host factors and facilitating chromatin remodeling.
4. Histone modifications: Histones, the protein components of chromatin, undergo various modifications that alter their structure and function. Adenoviruses induce specific histone modifications, such as acetylation and methylation, to create an open and transcriptionally active chromatin environment.
5. Formation of viral replication centers: As the viral chromatin becomes more accessible, viral genes are transcribed, and viral replication centers are formed. These replication centers are distinct nuclear domains where viral DNA replication and transcription occur efficiently.
By remodeling the chromatin structure of their genome, incoming adenoviruses establish a transcriptionally permissive environment that supports efficient viral gene expression and replication. These intricate chromatin changes are crucial for the virus to take control of the host cell's machinery and successfully complete its replication cycle.
