A steroid receptor coactivator acts as the DNA-binding partner of the methoprene-tolerant protein in regulating juvenile hormone response genes

Abstract

Methoprene-tolerant (Met) protein is a juvenile hormone (JH) receptor in insects. JH-bound Met forms a complex with the βFtz-F1-interacting steroid receptor coactivator (FISC) and together they regulate JH response genes in mosquitoes. Both proteins contain basic-helix-loop-helix (bHLH) and PAS motifs. Here we demonstrated that FISC is the obligatory partner of Met for binding to JH-response elements (JHREs). Met or FISC alone could not bind a previously characterized JHRE, while formation of the Met-FISC complex was necessary and sufficient to bind to the JHRE. This binding required participation of the DNA-binding domains of both Met and FISC. The optimal DNA sequence recognized by Met and FISC contained a core consensus sequence GCACGTG. While formation of the Met-FISC complex in mosquito cells was induced by JH, heterodimerization and DNA binding of bacterially expressed Met and FISC were JH-independent, implying that additional mosquito proteins were required to modulate formation of the receptor complex.

Juvenile hormone-activated phospholipase C pathway enhances transcriptional activation by the methoprene-tolerant protein

“…pCMA, pCMA-GAL4, pCMA-GAD, pCMA-GBD, and UAS×4-188-cc-Luc were from Lucy Cherbas (Indiana University, Bloomington, IA) (50). The construction of pCMA-AaMET (amino acids 1-977), pCMAAaTAI (amino acids 1-1,488), and 4×JHRE1-luc has been described previously (9,12). The Renilla luciferase construct pRL-CMV (Promega) was included as an internal control to normalize for variations in transfection efficiency.…”

“…Transfection was performed as described by Li et al (12). At 24 h after transfection, inhibitors and JH-III were added to the culture medium.…”

“…For simplicity, we will use a single name, Taiman, to describe all its orthologs in insects. TAI acts as the DNA-binding partner of MET; the MET-TAI complex recognizes an E-box-like sequence (5′-GCACGTG-3′) in the regulatory regions of JH-responsive genes, leading to the transcriptional activation of these genes (12). This function of MET-TAI in the JH-induced gene expression seems to be evolutionarily conserved in Ae.…”

Protein kinase C modulates transcriptional activation by the juvenile hormone receptor methoprene-tolerant

“…In the presence of JH, MET binds to another bHLH-PAS domain protein called Taiman (TAI) (also known previously as FISC in Aedes aegypti and SRC in Tribolium castaneum ) (Charles et al, 2011; Li et al, 2011; Zhang et al, 2011). TAI acts as the obligatory DNA binding partner of MET; the MET-TAI complex recognizes an E-box like sequence (5′-GCACGTG-3′) in the regulatory regions of JH target genes, leading to their transcriptional activation (Kayukawa et al, 2012; Li et al, 2014). In adult female Ae.…”

Krüppel Homolog 1 Inhibits Insect Metamorphosis via Direct Transcriptional Repression of Broad-Complex, a Pupal Specifier Gene

“…Our understanding of the molecular mechanism of JH-mediated repression of insect metamorphosis has significantly advanced (2): JH carried to a target cell is received by a JH receptor, methoprene tolerant (Met) (3)(4)(5)(6); JH-liganded Met interacts with steroid receptor coactivator (7)(8)(9)(10)(11)(12); the JH/Met/ steroid receptor coactivator complex activates Krüppel homolog 1 (Kr-h1), a repressor of metamorphosis, by interacting with a JH response element (kJHRE) in the Kr-h1 gene (9,10,(12)(13)(14)(15); Kr-h1 represses the larval-pupal metamorphosis (16 -20). To date, however, the mechanism of the repression of metamorphosis by Kr-h1, including target gene(s), binding site(s), and partner(s), has remained unknown.…”