First published online July 27, 2006
Development 133, 1602e (2006)
© The Company of Biologists Limited
Cyclin to the terminal
Several cyclins are responsible for regulating the cell cycle, but their
regulatory plasticity makes their distinct roles difficult to define. On
p. 3201, Jacobs and
colleagues discuss the particularly puzzling case of Cyclin A, which is
essential for Drosophila embryonic viability but is needed only for
certain types of mitoses. In the embryonic ectoderm, Cyclin A is only required
for the very last division before cells become post-mitotic. The researchers
have found that this is because during normal mitotic cycles, Cyclin A and
Cyclin E function redundantly to prevent the premature activity of
Fizzy-related/Cdh1 (Fzr), which targets the B-type Cyclins and String/Cdc25
for degradation. By contrast, before terminal mitoses, Cyclin E is inactivated
early, leaving Cyclin A to work alone - this means that in Cyclin A mutants
untimely Fzr activation prevents completion of the division programme.
Observations from other labs, and those made in this paper, indicate that
Cyclin A is also crucial for terminal mitoses in neuroblast lineages.
Related articles in Development:
- Terminal mitoses require negative regulation of Fzr/Cdh1 by Cyclin A, preventing premature degradation of mitotic cyclins and String/Cdc25
- Achim Reber, Christian F. Lehner, and Henning W. Jacobs
Development 2006 133: 3201-3211.
[Abstract]
[Full Text]
