Humanizing Protein Splicing Human immunity uses a
posttranslational modification previously shown in plants
and yeast By Sam Jaffe
James Yang, a surgeon working at the National Cancer
Institute in Bethesda,
Md., looked despondently at a patient's chest CT scan in
1998. Most of Yang's patients have late stage
metastasized renal cancer; few of them survive. By the
looks of the scan, this patient was in trouble.
Metastasized tumors bloomed throughout his chest.
One spot on the scan caught Yang's eye, though. While most
of the lung tumors were growing, one had shrunk noticeably
since the last scan. Yang circled the regressing tumor with
his grease pen, making a mental note to ask the thoracic
surgeon to save a tissue sample from that odd tumor. The
surgery was successful and the patient lived a few more
years before finally succumbing to his disease. But the CD8+
cytotoxic T cells taken from that one tumor would go on to
serve as the basis for a discovery with implications for
immunology and possibly all of molecular biology.
Yang and his research fellow Ken-Ichi Hanada identified a
cellular process in that tissue sample that had never before
been seen in vertebrates, no less in humans.1 Protein
splicing was occurring in the cells of that regressing
tumor. In an immunological trick, some cellular mechanism
removed multiple amino acids from a protein and re-ligated
the open carboxyl and amino termini to produce an antigen
for presentation. Though such protein editing events have
been noted in bacteria, archaea, yeast, and plants, this is
the first evidence of protein splicing in vertebrates
Read the rest at The Scientist.com the-the-Open ↗
scientist.com/yr2004/jun/research2_040607.html
Posted by Robert Karl Stonjek.