apoptosis

[Ian A. York]

In article <3pg0v7$1bco at aix1.segi.ulg.ac.be> hanon at stat.fmv.ulg.ac.be (Emmanuel Hanon) writes:
>Some viruses are able to induce apoptosis in some cell line. 
>Is there somebody who can explain me the interest of those viruses to 
>induce this type of cell death and the possible mechanism(s) of action.  

I think you have the situation backward.  In fact, the apoptosis that's 
induced is in the interest of the cell, and many viruses have gene 
products which inhibit apoptotic death.  I think the rationale for the 
cell undergoing death before the virus can complete its replication cycle 
is clear.  One might ask rather why viruses permit any cells to undergo 
apoptosis, and the answer is probably, because they con't block 
everything.  

As for mechanisms of action, since apoptosis induction is itself poorly 
understood, I doubt that a detailed molecular explanation is possible 
yet.  However, consider that many viruses massively alter cell cycle 
regulatory proteins, ranging from p53 to Rb and other members of the 
family, as well as cyclins and God knows what else; much apoptosis is 
apparently correlated to perturbation of cell cycle control, so I think 
that this is one major mechanism.

As for viral inhibition of apoptosis, this can be seen with adenoviruses 
(several proteins, including the E1b 19k protein); baculovirus; pox 
viruses, perhaps, which synthesize an protein which inhibits ICE (at 
least in vitro); and some of the herpesviruses.  I suspect that clsoer 
examination of other viruses will reveal apoptosis inhibitors in just 
about every class.

Ian

-- 
Ian York   (york at mbcrr.harvard.edu)
Dana-Farber Cancer Institute, 44 Binney St., Boston MA 02115
Phone (617)-632-3921     Fax  (617)-632-2627