Synthesis of a secretory protein and the points at which the process may be regulated are being investigated using a pair of spider fibroin glands as a model system. The two outstanding characteristics of the system are that the glands can be cultured in vitro, and that through simple manipulations their synthetic activity may be virtually turned off, and then stimulated into a massive production of the protein product. Having characterized the gland, its product and also the template molecule, we have, thus far, been elucidated. All of them exert their regulation on a translational level, one at elongation, the other at the readout now to move on in our characterization, into posttranscriptional regulation. This is justified, because within an early transient wave of macromolecular syntheses preceding the template production, di novo synthesis of small nuclear RNAs and positive strong signals for a U1 RNA probe have been both detected in the stimulated glands. These results indicate that within the orchestration of fibroin production, the small RNAs play a vital role. Small RNAs are currently in the limelight of gene expression because of their proven role(s) in the postranscriptional processing of transcripts in eukaryotes. We, therefore, aim to characterize the small RNAs, particularly the U ones, because of their well established roles as transcript maturators. In view of our preliminary observations, we will explore the system for tissue specific expressions of these molecules, and establish kinetic correlations between selective U gene expressions and elicited fibroin synthesis.