Unformatted text preview: n, the normal programmed cell deaths did not take place. A third gene,
ced-9, functioned as a negative regulator of apoptosis. If ced-9 was inactivated by mutation, the cells that would normally survive failed to do so.
Instead, they also underwent apoptosis, leading to death of the developing
animal. Conversely, if ced-9 was expressed at an abnormally high level, the
normal programmed cell deaths failed to occur. Further studies indicated
that the proteins encoded by these genes acted in a pathway with Ced-4 acting to stimulate Ced-3, and Ced-9 inhibiting Ced-4 (Figure 17.3). Genes
related to ced-3, ced-4, and ced-9 have also been identified in Drosophila and
mammals and found to encode proteins that represent conserved effectors
and regulators of apoptosis induced by a variety of stimuli. Caspases: The Executioners of Apoptosis
The molecular cloning and nucleotide sequencing of the ced-3 gene indicated that it encoded a protease, providing the first insight into the molecular mechanism of apoptosis. We no...
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