The tissue-specific expression of silkworm cuticle protein gene ASSCP2 is mediated by the Sox-2 transcription factor

The silk gland of silkworm is a unique organ in which silk proteins are synthesized, secreted, and transformed into fibers. The anterior silk gland (ASG) is located at the end of the silk gland, and is thought to be involved in silk fibrosis. In our previous study, a cuticle protein, ASSCP2, was identified. This protein is specifically and highly expressed in the ASG. In this work, the transcriptional regulation mechanism of ASSCP2 gene was studied by a transgenic route. The ASSCP2 promoter was analyzed, truncated sequentially, and used to initiate the expression of EGFP gene in silkworm larvae. After egg injection, seven transgenic silkworm lines were isolated. Molecular analysis revealed that the green fluorescent signal could not be detected when the promoter was truncated to -257 bp, suggesting that the -357 to -257 sequence is the key region responsible for the transcriptional regulation of the ASSCP2 gene. Furthermore, an ASG specific transcription factor Sox-2 was identified. EMSA assays showed that Sox-2 binds with the -357 to -257 sequence, and thus regulates the tissuespecific expression of ASSCP2. This study on the transcriptional regulation of ASSCP2 gene provides theoretical and experimental basis for further studies of the regulatory mechanism of tissue-specific genes.