title: Basic helix-loop-helix transcription factor Bmsage is involved in regulation of fibroin H-chain gene via interaction with SGF1 in Bombyx mori.
abstract: Silk glands are specialized in the synthesis of several secretory proteins. Expression of genes encoding the silk proteins in Bombyx mori silk glands with strict territorial and developmental specificities is regulated by many transcription factors. In this study, we have characterized B. mori sage, which is closely related to sage in the fruitfly Drosophila melanogaster. It is termed Bmsage; it encodes transcription factor Bmsage, which belongs to the Mesp subfamily, containing a basic helix-loop-helix motif. Bmsage transcripts were detected specifically in the silk glands of B. mori larvae through RT-PCR analysis. Immunoblotting analysis confirmed the Bmsage protein existed exclusively in B. mori middle and posterior silk gland cells. Bmsage has a low level of expression in the 4th instar molting stages, which increases gradually in the 5th instar feeding stages and then declines from the wandering to the pupation stages. Quantitative PCR analysis suggested the expression level of Bmsage in a high silk strain was higher compared to a lower silk strain on day 3 of the larval 5th instar. Furthermore, far western blotting and co-immunoprecipitation assays showed the Bmsage protein interacted with the fork head transcription factor silk gland factor 1 (SGF1). An electrophoretic mobility shift assay showed the complex of Bmsage and SGF1 proteins bound to the A and B elements in the promoter of fibroin H-chain gene(fib-H), respectively. Luciferase reporter gene assays confirmed the complex of Bmsage and SGF1 proteins increased the expression of fib-H. Together, these results suggest Bmsage is involved in the regulation of the expression of fib-H by being together with SGF1 in B. mori PSG cells.
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Qiong-Yan
authors.initials: QY
authors.lastname: Li
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Wen-Bo
authors.initials: WB
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Meng-Ting
authors.initials: MT
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Hong-Yi
authors.initials: HY
authors.lastname: Nie
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Yin-Xia
authors.initials: YX
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Zhang-Chuan
authors.initials: ZC
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China; Key Sericultural Laboratory of the Ministry of Agriculture, College of Bio-Technology, Southwest University, Chongqing, China.
authors.forename: Qing-You
authors.initials: QY
authors.lastname: Xia
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D012831:Bombyx / Q000235:genetics*; D005349:Fibroins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D005349:Fibroins; D019476:Insect Proteins; D015534:Trans-Activators; C093174:silk gland factor-1
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