Academic Publications / Travis J Bernardo, PhD

Genes & Development • 15th March 2017

Regulatory functions and chromatin loading dynamics of linker histone H1 during endoreplication in Drosophila. - PubMed - NCBI

Eukaryotic DNA replicates asynchronously, with discrete genomic loci replicating during different stages of S phase. Drosophila larval tissues undergo endoreplication without cell division, and the latest replicating regions occasionally fail to complete endoreplication, resulting in underreplicated domains of polytene chromosomes. Here we show that linker histone H1 is required for the underreplication (UR) phenomenon in Drosophila salivary glands. H1 directly interacts with the Suppressor of UR (SUUR) protein...

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Scientific Reports • 30th September 2016

BEN domain protein Elba2 can functionally substitute for linker histone H1 in Drosophila in vivo. - PubMed - NCBI

Metazoan linker histones are essential for development and play crucial roles in organization of chromatin, modification of epigenetic states and regulation of genetic activity. Vertebrates express multiple linker histone H1 isoforms, which may function redundantly. In contrast, H1 isoforms are not present in Dipterans, including D. melanogaster, except for an embryo-specific, distantly related dBigH1. Here we show that Drosophila BEN domain protein Elba2, which is expressed in early embryos and was hypothesized to have insulator-specific functions, can compensate for the loss of H1 in vivo. Although the Elba2 gene is not essential, its mutation causes a disruption of normal internucleosomal spacing of chromatin and reduced nuclear compaction...

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Nucleic Acids Research • 15th September 2014

A view through a chromatin loop: insights into the ecdysone activation of early genes in Drosophila. - PubMed - NCBI

The early genes are a key group of ecdysone targets that function at the top of the signaling hierarchy. In the presence of ecdysone, early genes exhibit a highly characteristic rapid and powerful induction that represents a primary response. Multiple isoforms encoded by early genes then coordinate the activation of a larger group of late genes. While the general mechanism of ecdysone-dependent transcription is well characterized, it is not known whether a distinct mechanism governs the hormonal...

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Advances in Insect Physiology • 25th April 2014

The Juvenile Hormone Receptor and Molecular Mechanisms of Juvenile Hormone Action

Juvenile hormone (JH) is a critical regulator of insect development and physiology, widely known for its ability to delay metamorphosis. The mechanisms underlying the action of JH have been poorly understood, partly as a result of difficulties identifying the JH receptor. However, the last few years have seen a rapid expansion of knowledge surrounding JH signalling. Ultraspiracle (USP), a nuclear receptor that was once considered as a possible receptor to JH, instead appears to function as a receptor to the JH precursor methyl farnesoate. The bHLH–PAS protein Methoprene-tolerant (Met) has now emerged as the principal receptor for JH...

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Insects • 22nd March 2012

Molecular Mechanisms of Transcription Activation by Juvenile Hormone: A Critical Role for bHLH-PAS and Nuclear Receptor Proteins. - PubMed - NCBI

Juvenile hormone (JH) is responsible for controlling many biological processes. In several insect species JH has been implicated as a key regulator of developmental timing, preventing the premature onset of metamorphosis during larval growth periods. However, the molecular basis of JH action is not well-understood. In this review, we highlight recent advances which demonstrate the importance of transcription factors from the bHLH-PAS and nuclear receptor families in mediating the response to JH.

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Journal of Biological Chemistry • 2nd March 2012

The Drosophila juvenile hormone receptor candidates methoprene-tolerant (MET) and germ cell-expressed (GCE) utilize a conserved LIXXL motif to bind... - PubMed - NCBI

Juvenile hormone (JH) has been implicated in many developmental processes in holometabolous insects, but its mechanism of signaling remains controversial. We previously found that in Drosophila Schneider 2 cells, the nuclear receptor FTZ-F1 is required for activation of the E75A gene by JH. Here, we utilized insect two-hybrid assays to show that FTZ-F1 interacts with two JH receptor candidates, the bHLH-PAS paralogs MET and GCE, in a JH-dependent manner. These interactions are severely reduced when helix 12 of the FTZ-F1 activation function 2 (AF2) is removed...

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Journal of Biological Chemistry • 23rd September 2011

The Drosophila FTZ-F1 nuclear receptor mediates juvenile hormone activation of E75A gene expression through an intracellular pathway. - PubMed - NCBI

Juvenile hormone (JH) regulates a wide variety of biological activities in holometabolous insects, ranging from vitellogenesis and caste determination in adults to the timing of metamorphosis in larvae. The mechanism of JH signaling in such a diverse array of processes remains either unknown or contentious. We previously found that the nuclear receptor gene E75A is activated in S2 cells as a primary response to JH. Here, by expressing an intracellular form of JH esterase, we demonstrate that JH

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Journal of Molecular Biology • 10th April 2009

Hormonal regulation of the E75 gene in Drosophila: identifying functional regulatory elements through computational and biological analysis. - PubMed - NCBI

Drosophila development is regulated by two hormones, 20-hydroxyecdysone (ecdysone) and juvenile hormone. We previously found that expression of the E75 gene is induced by both hormones in cultured S2 cells. E75 occupies over 100 kb of genomic DNA; it has four alternative promoters producing isoforms E75A, E75B, E75C, and E75D. To identify hormone response elements in the 60-kb noncoding area upstream of the E75A transcription start site...