Transcriptional regulatory elements in the upstream and intron of the fibroin gene bind three specific factors POU-M1, Bm Fkh and FMBP-1.
The transcriptional modulator in the fibroin gene intron is composed of multiple octamer-like AT-rich elements, to which several specific DNA-binding proteins named fibroin-modulator-binding proteins (FMBPs) bind. Three major FMBPs in the silk gland were characterized. Two of them (FMBP-2 and -3) were identified as a Fork head homologue (Bm Fkh) and a POU-domain protein (POU-M1) respectively. These factors were expressed in the silk gland with distinct temporal- and spatial-specificities during late larval development as well as during embryogenesis, and did not correlate directly with fibroin gene expression. The other (FMBP-1) appeared to correlate with the expression of the fibroin gene for temporal- and spatial-specificity. These FMBPs also bind to the elements in the upstream modulator. Transcriptional enhancement by both modulators was inhibited by binding competition for these factors with oligonucleotides. These results suggest that expression of the fibroin gene is controlled by co-ordination of these factors with distinct specificities during silk-gland development.
Takiya
S
S
National Institute for Basic Biology and Graduate University for Advanced Studies, Myodaiji, Okazaki, Japan.
Kokubo
H
H
Suzuki
Y
Y
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D012831:Bombyx / Q000196:embryology / Q000378:metabolism*; D003001:Cloning, Molecular; D018983:DNA Footprinting; D015342:DNA Probes / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005349:Fibroins / Q000235:genetics*; D051858:Forkhead Transcription Factors; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D007301:Insect Hormones / Q000378:metabolism; D019476:Insect Proteins; D009687:Nuclear Proteins / Q000378:metabolism*; D050809:POU Domain Factors; D017421:Sequence Analysis; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology
D015342:DNA Probes; D004268:DNA-Binding Proteins; D051858:Forkhead Transcription Factors; D007301:Insect Hormones; D019476:Insect Proteins; D009687:Nuclear Proteins; D050809:POU Domain Factors; C085604:POU-M1 protein, Bombyx mori; D014157:Transcription Factors; D005349:Fibroins