Enhancer activity ofHelitroninsericin-1gene promoter fromBombyx mori

Abstract

Sericin is a kind of water-soluble protein expressed specifically in the middle silk gland of Bombyx mori. When the sericin-1 gene promoter was cloned and a transgenic vector was constructed to express a foreign protein, a specific Helitron, Bmhel-8, was identified in the sericin-1 gene promoter sequence in some genotypes of Bombyx mori and Bombyx mandarina. Given that the Bmhel-8 Helitron transposon was present only in some genotypes, it could be the source of allelic variation in the sericin-1 promoter. The length of the sericin-1 promoter sequence is approximately 1063 or 643 bp. The larger size of the sequence or allele is ascribed to the presence of Bmhel-8. Silkworm genotypes can be homozygous for either the shorter or larger promoter sequence or heterozygous, containing both alleles. Bmhel-8 in the sericin-1 promoter exhibits enhancer activity, as demonstrated by a dual-luciferase reporter system in BmE cell lines. Furthermore, Bmhel-8 displays enhancer activity in a sericin-1 promoter-driven gene expression system but does not regulate the tissue-specific expression of sericin-1.

Transposable elements as evolutionary driving force to ecological speciation in cactophilicDrosophilaspecies

“…Indeed, we observed that Helitrons represent 50% of all cases. These elements have been extensively reported on promoter regions of other eukaryotic species (102)(103)(104)(105), in which a few cases of embedded TFBSs were reported (106,107). Here, we demonstrated that part of the enrichment in TEs observed at the promoter region of ORs might be due to the exaptation of TFBSs mostly derived from Helitrons.…”

“…Helitrons have been extensively reported as a source of TFBSs when located at the promoter region of genes. In the bat Myotis lucifugus , 1.4% of the transcripts from the salivary gland have Helitron -derived sequences, for which ∼6% correspond to promoters (103). In the plant Brassica napus , an Helitron insertion disrupts the ancestral promoter of the gene BnSP11-1 , altering the mating system of the populations carrying this insertion, which in turn contributes to the adaptation and speciation (119).…”

Leap forward with insect genomics

“…Huang et al . cloned a specific helitron, Bmhel‐8, from the sericin‐1 gene promoter sequence and showed that Bmhel‐8 exhibits enhancer activity in a sericin‐1 promoter‐driven gene expression system, but does not influence tissue‐specific expression of sericin‐1 (Huang et al ., ). Lu et al .…”