Hexim1, also known as hexamethylene bis-acetamide inducible 1, is a protein that acts as a tumor suppressor and is involved in the regulation of innate immunity. It was initially described as a non-coding RNA-dependent regulator of transcription. Hexim1 binds to 7SK RNA and inhibits the positive transcription elongation factor (P-TEFb), thus playing a role in controlling transcription elongation. It is also involved in regulating the stability of transcription factor components and their binding to targets. Additionally, it participates in pathways related to erythropoiesis, cell cycle regulation, and hormone-related gene expression, with implications for diseases like cancer, AIDS, cardiac hypertrophy, and inflammation [1,3,4,5].

In human erythropoiesis, HEXIM1 is a key transcription regulator. Overexpression of HEXIM1 promotes erythroid proliferation and fetal globin expression. It regulates erythroid proliferation by influencing RNAPII pausing at cell cycle checkpoint genes and increasing RNAPII occupancy at genes promoting cycle progression. Genome-wide profiling shows changes in the distribution of GATA-binding factor 1 (GATA1) and RNAPII, especially at the β-globin loci, affecting fetal globin expression [2]. In alpha-herpesvirus (Anatid herpesvirus 1) infection, HEXIM1 is significantly upregulated. Excessive HEXIM1 assists the virus in progeny virus production, gene expression, and RNA polymerase II recruitment by promoting the formation of more inactive P-TEFb and loss of RNAPII S2 phosphorylation, while suppressing some host survival-related genes [6].

In conclusion, Hexim1 is an essential regulator in multiple biological processes. Its role in diseases such as those related to abnormal cell proliferation (cancer), viral infections (AIDS-related HIV transcription), and cardiac disorders (hypertrophy) is significant. Functional studies, especially those related to its role in transcription elongation and cell-cycle-related processes, contribute to our understanding of disease mechanisms. The insights from studies like those on its function in erythropoiesis and viral infections help in potentially developing therapeutic strategies for relevant diseases.