PTRF (Polymerase I and Transcript Release Factor) is a gene that was initially thought to code for a protein that functioned only as a transcription factor. The PTRF protein regulates rRNA transcription by promoting the dissociation of transcription complexes and the reinitiation of polymerase I on nascent rRNA transcripts. However, this is not the only function of the PTRF protein. Recent findings have revealed that the protein also plays a very important role in the formation of caveloae. Caveolae are small indentations on the surface of muscle, bone, fat, and immune cell membranes, that have been implicated in several functions, including cell signaling, lipid regulation, and endocytosis. The PTRF protein is required for formation of caveola, hence it is now known as PTRF-CAVIN. Interestingly, this protein is also thought to modify insulin-regulated gene expression. It has been shown that the PTRF-CAVIN protein translocates from the caveola to the cytoplasm following insulin stimulation.

Mutations in the PTRF gene have been shown to cause a form of Congenital Generalized Lipodystrophy, characterized by generalized lipodystrophy, muscular dystrophy, and insulin resistance.

The PTRF-CAVIN gene is located on chromosome 17. It covers a length of about 21 Kb. The protein itself is 390 amino acids long, and weighs about 43 KDa. The gene is expressed in various tissues. However, maximum expression levels are seen in adipocytes, smooth, heart and skeletal muscles, and osteoblasts. Neuronal tissue shows almost no expression.