Cell cycle cyclin

Cell cycle is one of the physiological processes in which the role of uhiquitin—proteasome-mediated proteolysis is well established. With the advent of yeast mutants that interfered with various phases of the cell cycle, cyclin-dependent kinases (Cdks) were found to have a critical role in regulating the cell cycle. Typically, Cdks activated hy regulatory proteins are known as cyclins. Different Cdk—cyclin complexes are formed at specific stages of the cell cycle such as the S-phase (in which DNA synthesis occurs) and the metaphase. The transition from metaphase to anaphase depends on degradation of cyclins. " " Systematic biochemical studies showed that cyclins were substrates for the uhiquitin—proteasome pathway (Table 5). 

Figure 21.15 Regulation of three genes that express proteins essential for cell cycle. The same transcription factor activates three genes that encode for (1) DNA polymerase (2) a cell cycle cyclin (3) tetra hydrofolate reductase.

Fig. 13.6 Concentration changes in cyclins during the cell cycle. Cyclins of types D, A, E, and B show characteristic concentration changes in the course of the cell cycle. The figure depicts the approximate...

Cell Cycle Control. Figure 1 Cell cycle regulation by Cyclin dependent kinases (CDKs). Different cyclins bound to different CDKs promote the transition from one cell cycle phase into another. CDK-dependent phosphorylation of Rb is required to release active E2F transcription factors, which promotes entry into S phase. 

The rationale behind CDK inhibition during anticancer treatment is to stop hyperactive cell cycles and to inhibit the activity of cyclins that are frequently overexpressed in human cancer. 

Rowley, A., Johnston, G.C., Butler, B., Werner-Washbume, M., Singer, R.A. (1993). Heat shock-mediated cell cycle blockage and G1 cyclin expression in the yeast saccomyces cerevisiae. Mol. Cell. Biol. 13, 1034-1041. 

Othet cyclins and CDKs are involved in different aspects of cell cycle progression (Table 36-7). Cychn E and CDK2 form a complex in late Gl. Cychn E is tapidly degraded, and the released CDK2 then fotms a complex with cyclin A. This sequence is necessaty fot the initiation of DNA synthesis in S phase. A complex between cychn B and CDKl is tate-hmiting fot the G2/M transition in eukatyotic cells. 

Figure 36-21. Schematic illustration of the points during the mammalian cell cycle during which the indicated cyclins and cyclin-dependent kinases are activated. The thickness of the various colored lines is indicative of the extent of activity.

Table 36-7. Cyclins and cyclin-dependent kinases involved in cell cycle progression.

PALOZZA P, SERINI S, MAGGIANO N, ANGELINI M, BONINSEGNA A, DI NICUOLO F, RANELLETTI F O and CALVIELLO G (2002) Induction of cell cycle arrest and apoptosis in human colon adenocarcinoma cell lines by P-carotene through down-regulation of cyclin A and Bcl-2 family proteins , Carcinogenesis, 23, 11-18. 

BCL-1 or PRAD1 Codes for cyclin D1, a cell cycle clock stimulator Breast, head and neck cancers... 

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