Architectural factor HMGA induces promoter bending and recruits C/EBP and GATA during silkmoth chorion gene regulation

Abstract

A protein displaying significant similarity to mammalian HMGA (high-mobility group A) proteins, but also bearing unique structural features, was isolated from silkmoth (Bombyx mori) follicular cells. This factor, named BmHMGA, exhibits specific binding preference for chorion gene promoter elements and induces DNA bending thereon. BmHMGA deploys temporal-specific interaction with transcription factors BmC/EBP (C/EBP is CCAAT/enhancer-binding protein) and BmGATAβ during follicle maturation. The respective protein complexes can be detected on chorion gene promoters in vivo, with different developmental profiles each time. Analogous interaction takes place on the putative promoter of the BmC/EBP gene, hinting towards a transcriptional circuit that is responsible for the progress of choriogenesis as a whole. Finally, transient suppression of BmHMGA expression led to down-regulation of chorion genes and the BmC/EBP gene, and revealed recruitment of BmC/EBP, BmGATAβ and TFIID (transcription factor IID)/TBP (TATA-box-binding protein) by BmHMGA. A revised model for chorion gene regulation is discussed in view of these findings.

Unscrambling butterfly oogenesis

“…The D. melanogaster ortholog of C/EBP is slbo , which is also expressed in follicle cells though predominantly involved in border cell migration (references in Additional file 1). High mobility group protein A (HMGA) is essential for B. mori choriogenesis as it induces chorion gene promoter bending and recruits C/EBP and GATAbeta [176]. Pararge aegeria expressed C/EBP (i.e.…”

Silkmoth chorion gene regulation revisited: promoter architecture as a key player

“…, 2003). Similar data of an antagonistic C/EBP‐GATA relation were also produced by ChIP on middle promoters, where GATA binding correlated with down‐regulation (Papantonis et al. , 2008b).…”

“…The former rely upon an interaction of the C/EBP protein dimer with an early‐type cis ‐element (lower affinity), the latter (lagging in developmental time) on a late‐type:C/EBP (higher affinity) interaction (A. Papantonis and R. Lecanidou, unpubl. data; Papantonis et al. , 2008a, b; Papantonis & Lecanidou, 2009).…”

CHD1 Assumes a Central Role during Follicle Development

“…As a conclusion, chorion gene expression is regulated in many levels. It is dependent on C/EBP assuming an activator/repressor role, 6 on HMGA acting as the initial recruiter of other protein factors, 40 and on CHD1 function for nucleosome repositioning and H3K4 methylation.…”

“…Analogous observations were made for early and late specific chorion genes (data not shown). We also performed ChIP assays using specific antisera raised against architectural factor HMGA, 40 di-/ trimethylated lysine 4 of histone H3, and the basal transcriptional machinery factor TFIID/TBP. Apart from the apparent correlation between the patterns of appearance of H3K4me2/3 and TFIID (shown in Fig.…”