We have isolated and characterized a zinc finger-containing
cDNA (ZSG-1) from the middle
silk gland of Bombyx mori. Sequence analysis indicates that the
protein encoded by the ZSG-1 transcript contains a domain of five fingers similar to the zinc finger repeats of the Xenopus
transcription factor TFIIIA, the product of Drosophila segment polarity gene cubitus interruptus (ci) and the human zinc finger
protein GLI, which has been found to be amplified in several human
glioblastomas. The transcript expression pattern and
protein distribution of ZSG-1 during embryogenesis and
silk gland development were analyzed by northern blot and immunohistochemistry. ZSG-1 transcript was most strongly detected in the middle
silk gland and weakly in the posterior
silk gland at the fourth larval intermolt and molting stages. When the larvae entered the fifth intermolt, the expression of ZSG-1 rapidly decreased by 2 days after the fourth ecdysis and maintained a low level thereafter in the middle
silk gland, while the transcript in the posterior
silk gland gradually became undetectable. The transcript was first detected at around stage 18 of early embryogenesis; it then increased to the maximum level by stage 27 and maintained a high level until hatching. Interestingly, the ZSG-1
protein was most strongly distributed in the middle
silk gland during embryonic
silk gland development. The expression of ZSG-1 in the
silk glands suggests that this gene may play important roles in the development of
silk gland.