Transmethylation reaction is essential for Sarcophaga lectin gene activation

Incubation of Sarcophaga fat bodies in buffered insect saline resulted in simultaneous activation of multiple defense protein genes [Sugiyama, H. and Natori, S. (1991) Eur. J. Biochem. 200, 495-500]. In this study, we demonstrated that the addition of both adenosine and homocysteine thiolactone to this medium abolished activation of these defense protein genes. As S-adenosyl-homocysteine, a potent inhibitor of the transmethylation reaction, is produced in the fat body under these conditions, methylation of a certain fat body protein seems to be a prerequisite for the selective activation of insect defense protein genes. Activation of the HSP70 gene was not interfered with S-adenosyl-homocysteine.