Cdk8, or cyclin-dependent kinase 8, is a key member of the cyclin-dependent kinase family. It is associated with transcription regulation, acting as a "molecular switch" in the Mediator complex. Cdk8 phosphorylates transcription factors to regulate gene expression and can control the transcription process via the Mediator complex. It has been implicated in multiple biological processes and is considered a potential drug target for diseases like breast and prostate cancer [1,3,5,7].

In Drosophila, neuronal loss of Cdk8 severely reduces fly lifespan and causes bang sensitivity. Cdk8 promotes mitochondrial fission through Drp1 phosphorylation at S616. Intriguingly, overexpression of Cdk8 can suppress phenotypes in flies with low levels of Pink1, a mitochondrial kinase involved in Parkinson's disease [2]. In T cells, inhibition of Cdk8 and Cdk19 can convert antigen-specific effector/memory T cells into Foxp3-expressing Treg cells, suggesting its role in immunological diseases [4]. Cdk8 inhibitors can also antagonize HIV-1 reactivation and promote provirus latency in T cells [6].

In summary, Cdk8 is crucial for transcription-related processes, mitochondrial fission, and immune-related functions. Its study in models like Drosophila has provided insights into its role in lifespan, neurodegenerative-like phenotypes, and immunological and viral-related diseases. These findings suggest Cdk8 as a potential target for treating cancer, immunological disorders, and HIV-1-related conditions [1-4,9,10].