Host RNA polymerase II (RNA pol-II) is the major enzyme responsible for transcription of mRNA from a DNA template strand.
Some viruses interfere with host RNA pol-II function. They may either mediate its ubiquitination and subsequent proteasomal degradation, or inhibit RNA pol-II phosphorylation thereby lowering its efficiency. They can as well interfere with initiation factors. Inhibiting host transcription eventually leads to shutoff of host proteins expression and gives viruses transcripts a competitive edge for access to the cellular translation machinery. Preventing the expression of host proteins is also a strategy to counteract the antiviral response.
Viruses inhibiting transcription:
| Family | Virus | Viral protein | Transcription inhibition strategy | references |
| Herpesviridae | HHV-1 | ICP27 | RNA pol-II ubiquitination and proteasomal degradation |
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| ICP22 | Counteracts CTD Ser-2 phosphorylation |
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| Bunyaviridae | Bunyamwera virus | NSs | Counteracts CTD Ser-2 phosphorylation |
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| Orthomyxoviridae | Influenza virus | Polymerase PB1, PB2, PA | RNA pol-II ubiquitination and proteasomal degradation |
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| Orthomyxoviridae, Thogotovirus | Thogoto virus | ML | Inhibition of TFIIB |
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| Papillomaviridae, alphapapillomavirus | HPV16 | E7 | Inhibition of TBP |
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| Picornaviridae | Poliovirus | 3C | Cleavage of TBP |
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| Bunyaviridae, Phlebovirus | Rift valley fever virus | NSs | Downregulates TFIIH subunit p62 |
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| Herpesviridae | Varicella virus | IE63 | Disruption of the transcriptional pre-initiation complex |
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