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Tuesday, November 15, 2011

Cancer killing peptides


Researchers from USC and various Korean universities have identified two virus-derived peptides that can kill cancer cells.  The small viral proteins do this by mediating levels of the tumor suppressor protein known as p53.  To understand what’s going on, let’s meet the proteins involved.

When a protein with an apparent mass of 53 kilodaltons was first discovered in 1979, it had an unknown function.  The name p53 has stuck ever since, despite the fact that we now know it’s a tumor suppressor.  Among its functions is the initiation of apoptosis, or programmed cell death. It can also halt cell cycles during DNA repair to give the repair enzymes more time to correct errors.

Normally, p53 levels are low.  After all, the unnecessary slowing down or killing of cells would be wasteful.  There are various feedback mechanisms for controlling the levels of p53, including the action of a protein known as HAUSP.  The two peptides in this study, which were derived from Kaposi's sarcoma–associated herpesvirus, selectively bind to and inactivate HAUSP.  Without that protein, p53 levels are free to rise. More p53 means more cell death, which is a good thing when the cells in question are cancerous.

Needless to say, it's a long road between these experiments and any clinical applications.  Which is not to say that a practical usage won’t one day be found for these small peptides.

Position of the p53 gene on chromosome 17.