characterizes severe infections and the state of in- 
anition (cachexia) that is observed in cancer and 
other chronic illnesses. Assistant Investigator Bruce 
A. Beutler, M.D. (University of Texas Southwestern 
Medical Center at Dallas) and his co-workers are 
studying the regulation of cachectin/TNF biosynthe- 
sis, the processing of cachectin/TNF once it has 
been produced, and the mechanism of macrophage 
activation by bacterial endotoxin. 
JThe regulation of bacterial genes required for 
synthesis of the amino acid cysteine has been found 
to require a specific regulatory protein, CysB, 
which binds to the DNA of these genes. Acetylser- 
ine, which serves as a signal of cysteine deprivation, 
interacts with bound CysB protein and stimulates 
messenger RNA synthesis. In studies on mammalian 
sulfur metabolism, the laboratory of Investigator 
Nicholas M. Kredich, M.D. (Duke University) has 
cloned and sequenced DNA encoding the enzyme 
5-adenosylmethionine synthetase from rat liver. The 
product of the enzyme, 5-adenosylmethionine, is 
required for more than 100 different cellular reac- 
tions and is a key factor in DNA, RNA, and protein 
metabolism. 
12 
