Geminin

Geminin, DNA replication inhibitor, also known as GMNN, is a human gene.

Geminin is a protein with a dual role during eukaryotic cell cycle. Geminin was originally identified as a DNA replication inhibitor. Notwithstanding, recent experimental works show that Geminin can also promote DNA replication.

Geminin has two roles in two different phases of the cell cycle::

During S phase of the cell cycle Geminin is a negative regulator of DNA replication. Inhibition of Geminin during this phase (by RNAi) results in an extra round of replication of portions of the genome.

During M phase of the cell cycle (mitosis) Geminin stabilizes the replication factor Cdt1 promoting DNA replication during the following cell cycle. In fact, inhibition of Geminin during mitosis (by RNAi) leads to destabilization of Cdt1 protein and impairment of DNA replication during the following cell cycle.

Geminin therefore ensures that one and only one round of replication occurs during each cell cycle.

Recently, Geminin has been found to be overexpressed in several malignancies and cancer cell lines. This supports the notion that Geminin has also a positive role in DNA replication and cell cycle progression.

Geminin is a nuclear protein. The protein consists of about 200 residues.

Geminin is absent during G1 phase and accumulates through S, G2 and M phases of the cell cycle. Geminin levels drop at the metaphase/anaphase transition of mitosis.