The control of BhB10-1 gene expression in the salivary gland of Bradysia hygida (Diptera, Sciaridae) is disrupted in vivo by a delayed effect of cycloheximide.

BhB10-1 is an amplified gene present in DNA puff B10. This gene is very active in the salivary gland regions S1 and S3 at the end of the larval development. Two transcripts of this gene, 1.3 and 1.1 kb in size, were detected. A secretory protein, SP23, is the product of BhB10-1. In this work, we present evidence supporting the hypothesis that a biphasic process of mRNA degradation is an important component in the control of BhB10-1 gene expression. The 1.3 kb transcript, by a process of poly(A) tail shortening, is converted to the inactive transcript of 1.1 kb which is detected during and after the period of SP23 expression. Cycloheximide in very low concentration, if applied at a proper time, can disrupt this process leading to extended periods of 1.3 kb RNA detection and SP23 synthesis. A tentative model is proposed to explain this phenomenon.