The nuclear protein in testis gene encodes a 1,132-amino acid protein termed NUT that is expressed almost exclusively in the testes, ovaries, and ciliary ganglion (i.e. a parasympathetic ganglion of nerve cells located just behind the eye). NUT protein facilitates the acetylation of chromatin by histone acetyltransferase EP300 in testicular spermatids (cells that mature into sperms). This acetylation is a form of chromatin remodeling which compacts spermatid chromatin, a critical step required for the normal conduct of spermatogenesis, i.e. the maturation of spermatids into sperm. Male mice that lacked the mouse Nutm1 gene using a gene knockout method had abnormally small testes, lacked sperm in their cauda epididymis, and were completely sterile. These findings indicate that Nutm1 gene is essential for the development of normal fertility in male mice and suggest that the NUTM1 gene may play a similar role in men. BRD4 protein recognizes acetylated lysine residues on proteins and by doing so participates in the regulation of DNA replication, DNA transcription, and thereby key cellular processes involved in the development of neoplasms (i.e. malignant or benign tissue growths). The product of the BRD4-NUTM1 fusion gene, BRD4-NUT protein, stimulates the expression of at least 4 relevant genes, MYC, TP63, SOX2, and MYB in cultured cells. All four of these genes are oncogenes, i.e., genes that when overexpressed and/or overly active promote the development of certain types of cancers. It is generally accepted that the BRD4-NUT protein promotes these neoplasms by maintaining their neoplastic cells in a perpetually undifferentiated, proliferative state. Further studies are needed to confirm and expand these views and to determine if any of the overexpressed gene products of the BRD4-NUT protein contribute to the development and/or progression, or can serve as targets for the treatment, of the neoplasms associated with the BRD4-NUTM1 fusion gene. These questions also apply to a wide range of neoplasms that have more recently been associated with the NUTM1 gene fused to other genes.