Prohibitin

• OMIM: 176705

• MGI: 97572

Prohibitin (PHB ) is a protein in the cell membrane and the membrane of the mitochondria, and is found in all tissue types. Prohibitingene described in animals, fungi, plants and protozoa. The precise function of the protein is not known. Prohibitins be divided into two classes, which are called because of their resemblance to the Hefevarianten Prohibitins of type I or type II prohibitins. In all previously studied organisms has always found at least one Prohibitinvariante.

Prohibitins are evolutionarily highly conserved genes that are ubiquitously expressed. Prohibitingen the human, which is in the BRCA1 region of chromosome 17q21 was originally thought to be a negative regulator of cell proliferation and tumor suppressor. This anti-proliferative activity is today attributed to the 3 ' non-transcribed region of the lying PHB gene and not the protein coding region. Mutations in the human PHB gene have been associated with sporadic breast cancer. Prohibitingen of two mRNA splice variants are transcribed, differing in the length of the untranslated region at the 3 ' end of the gene. The longer transcript is found mainly in prolifererierendem tissue, the conjecture suggests that serves the 3 'untranslated region as a transactivating regulatory RNA.

Today, it is assumed the form prohibitins large annular protein complexes on the inner mitochondrial membrane and for the survival of multicellular organisms is essential. The exact function of the PHB complexes is not known, but it is suspected that they are either used as chaperones for the respiratory chain proteins or form a kind of backbone of the shape of the mitochondria. Recently, it was shown that in mice prohibitins and plants are more positive regulators of cell proliferation. Numerous publications have, however, evidence indicating that prohibitin in humans is a cell nucleus -associated repressor of the cell cycle by binding to the proliferation stimulated transcription factor E2F and inhibits its activity. However, these experiments were performed in most cases of transformed human cell lines and evidence, the prohibitins have this function in normal human tissues or in other organisms, yet were not found.