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Protein p27 , belonging to the family of inhibitors of cyclin-dependent kinase called CIP / KIP , is currently the subject of intensive research in the field of cell biology and pathomechanisms of proliferative processes , because it not only controls the cell cycle by regulating the activity of CDK -cyclin complexes , but also participates in the induction apoptosis. P27 regulates the activity of CDK -cyclin holoenzymów in two ways. First, it inhibits the kinase activity of the complexes . The crystallographic studies of a complex formed by the N -terminal fragment of p27 , CDK2 and cyclin kinase A suggests that the cause of the inhibition of the kinase complex is significant conformational changes in and around the catalytic pocket of the enzyme which lead to disruption of ATP connection process . Secondly, the p27 protein is involved in the formation of stable complexes of CDK4 -cyclin D1. It increases the affinity of cyclin D1 CDK4 , affects the level of synthesis of D -type cyclins in the cell , and the stability of cyclin D1 . Protein p27 is also involved in the transport of cyclin D1 and CDK4 to the nucleus . Recent studies also point to a more complex nature of the interaction between p27 and protein kinase complexes . The protein p27 is a regulator of the activity of one part holoenzymów CDK -cyclin , on the other hand the level of its concentration in a cell is indirectly controlled by a complex of CDK2 -cyclin E , which phosphorylates located at position 187, threonine p27 molecule . This phosphorylation is a signal to the proteolytic degradation of p27 protein by the 26S protease complex .
Relatively little is known about the influence while p27 to apoptosis . Not given a definitive answer to the question under which conditions, p27 induces programmed cell death , in which it inhibits .
In view of the important role of p27 in the control of normal cell proliferation and apoptosis, much attention lately disturbance level of its expression in malignancies . Expression of p27 inhibitor in tumors shows a common disorder : it is most often reduced compared to normal tissues , which may have prognostic importance . This information can be used to develop new therapeutic strategies .

The Editorial Board
Andrzej Łukaszyk - przewodniczący, Zofia Bielańska-Osuchowska, Szczepan Biliński, Mieczysław Chorąży, Aleksander Koj, Włodzimierz Korochoda, Leszek Kuźnicki, Aleksandra Stojałowska, Lech Wojtczak

Editorial address:
Katedra i Zakład Histologii i Embriologii Uniwersytetu Medycznego w Poznaniu, ul. Święcickiego 6, 60-781 Poznań, tel. +48 61 8546453, fax. +48 61 8546440, email:

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