Although gene regulatory mechanisms in eukaryotic cells are complex, some progress is being made in understanding them. Chromosomal proteins may play a significant role in genome function and gene control. More specifically, a central role may be played by the nuclear nonhistone proteins. It appears that both viral transformation and steroid hormone action may be associated with the phosphorylation of these proteins. Recent studies have revealed that some oncogenic viruses are capable of producing viral transforming proteins with protein kinase activity. This suggests how they may subvert normal gene regulatory mechanisms. Furthermore, the effects of the steroid-receptor complex on nuclear nonhistone proteins may be similar to the effects of these viral transforming proteins, but in a controlled sense. A model of gene-regulatory, nuclear phosphorylation reactions is formulated which suggests how some oncogenic viruses may control normal gene regulatory mechanisms and how steroid hormones may interact with these same mechanisms. Such a model may reveal how disruption of these same mechanisms leads to carcinogenesis.