Tumor suppressor gene

Tumor suppressors are proteins that control the cell cycle or induce apoptosis. Thus, the probability is high that developed a tumor cell in a multicellular when such a protein from a cell defect or deficiency. It is not so much the name of a protein function as a pathological definition.

A mutation or deletion of a tumor suppressor gene coding for a ( tumor suppressor gene ) increases the likelihood of tumor formation. In this sense, tumor suppressor genes have a similar effect as mutations in proto-oncogenes.

Functions

Tumor suppressor proteins have approximately the following functions:

  • Suppression of the gene expression of growth factors, resulting inhibition of the cell cycle and thus no further cell division.
  • Stopping the cell cycle if DNA damage. If the damage is found to be reversible, there is a continuing of the cell cycle.
  • If an irreversible DNA damage is present, the tumor suppressor gene initiates an apoptosis of the cell to protect the body from damage caused by the potential tumor cell.
  • Some of the proteins involved in cell adhesion prevent tumor cells from spreading in the body and inhibit the formation of metastases.

Examples

Examples of tumor suppressors are:

  • P16: This family of proteins inhibits CDKs and thus prevents a transfer from the G1 to S phase of the cell cycle.
  • P27: This protein controls the transition from G0 to G1 phase of the cell cycle and prevents this, if its synthesis is increased. Both of virus -infected cells promote a tissue mediators (TGF- β ) p27 formation, as well as neighboring cells in contact inhibition.
  • The pRB normally surrounds the shell-like transcription factor E2F, which is absolutely needed for the initiation of S phase. Phosphorylation opens gradually the shell, and the transcription factor is " released ". In tumor cells, the gene for the RB protein is mutated in over 60 % of cases. Regulating ( that is, the phosphorylation ) of the Rb protein is disturbed even in every tumor cell in any way.
  • The p53: This protein ensures that a cell divides only when their genetic material is also intact. This is not the case in a tumor cell. Then p53 shows two main effects: cell cycle arrest, and irreparable damage
  • The induction of apoptosis.
Deletion (genetics)
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