Biology subjects

Hodkinson, L. J.

Publications and source records attributed to Hodkinson, L. J..

5 recordsLinked to original sources

bioRxiv2024

Cis element length variability does not confer differential transcription factor occupancy at the D. melanogaster histone locus

Histone genes require precise regulation to maintain histone homeostasis and ensure nucleosome stoichiometry. Animal histone genes often have unique clustered genomic organization. However, there is variability of histone gene number and organization as well as differential regulation of the histone genes across species. The Drosophila melanogaster histone locus has unique organizational characteristics as it exists as a series of [~]100 highly regular, tandemly repeated arrays of the 5 replication-dependent histone genes at a single locus. Yet D. melanogaster are viable with only 12 transgenic histone gene arrays. We hypothesized that the histone genes across the locus are differentially regulated. We discovered that the GA-repeat within the H3/H4 promoter is the only variable sequence across the histone gene arrays. The H3/H4 promoter GA-repeat is targeted by CLAMP to promote histone gene expression. We also show two additional GA-binding transcription factors, GAGA Factor and Pipsqueak, target the GA-repeat. When we further examined CLAMP and GAF targeting, we determined that neither CLAMP nor GAF show bias for any GA-repeat lengths. Furthermore, we found that the distribution of GA-repeats targeted by both CLAMP and GAF do not change throughout early development. Together our results suggest that the transcription factors targeting the H3/H4 GA-repeat do not impact differential regulation of the histone genes, but indicate that future studies should interrogate additional cis elements or factors that impact histone gene regulation.

genetics↗

bioRxiv2023

Sequence reliance of a Drosophila context-dependent transcription factor

Despite binding similar cis elements in multiple locations, a single transcription factor often performs context-dependent functions at different loci. How factors integrate cis sequence and genomic context is still poorly understood and has implications for off-target effects in genetic engineering. The Drosophila context-dependent transcription factor CLAMP targets similar GA-rich cis elements on the X-chromosome and at the histone gene locus but recruits very different, loci-specific factors. We discover that CLAMP leverages information from both cis element and local sequence to perform context-specific functions. Our observations imply the importance of other cues, including protein-protein interactions and the presence of additional cofactors.

genetics↗

bioRxiv2023

A bioinformatics screen reveals Hox and chromatin remodeling factors at the Drosophila histone locus

Cells orchestrate histone biogenesis with strict temporal and quantitative control. To efficiently regulate histone biogenesis, the repetitive Drosophila melanogaster replication-dependent histone genes are arrayed and clustered at a single locus. Regulatory factors concentrate in a nuclear body known as the histone locus body (HLB), which forms around the locus. Historically, HLB factors are largely discovered by chance, and few are known to interact directly with DNA. It is therefore unclear how the histone genes are specifically targeted for unique and coordinated regulation. To expand the list of known HLB factors, we performed a candidate-based screen by mapping 30 publicly available ChIP datasets and 27 factors to the Drosophila histone gene array. We identified novel transcription factor candidates, including the Drosophila Hox proteins Ultrabithorax, Abdominal-A and Abdominal-B, suggesting a new pathway for these factors in influencing body plan morphogenesis. Additionally, we identified six other transcription factors that target the histone gene array: JIL-1, Hr78, the long isoform of fs(1)h as well as the generalized transcription factors TAF-1, TFIIB, and TFIIF. Our foundational screen provides several candidates for future studies into factors that may influence histone biogenesis. Further, our study emphasizes the powerful reservoir of publicly available datasets, which can be mined as a primary screening technique.

molecular biology↗

bioRxiv2022

MSL2 targets histone genes in Drosophila virilis

Histone genes are amongst the most evolutionary conserved in eukaryotic genomes, yet cis-regulatory mechanisms of histone gene regulation differ considerably amongst species. In Drosophila melanogaster, an interaction between GA-rich cis elements in the H3/H4 promoter and the GA-binding transcription factor CLAMP is important for promoting histone gene regulation and factor recruitment to the locus. CLAMP also participates in male dosage compensation by recruiting the Male Specific Lethal Complex (MSLc) to the X-chromosome. We discovered that the male-specific protein of MSLc, MSL2, is recruited to the autosomal major histone locus in D. virilis but not to the minor locus or to the single histone locus in other species. While the histone coding sequences are well conserved between species, the critical GA-rich cis elements in the H3/H4 promoter are poorly conserved between D. melanogaster and D. virilis. We show that CLAMP still targets the two D. virilis histone loci in vivo. Further, CLAMP interacts with the D. virilis H3/H4 promoter in vitro, even when the poorly-conserved GA-rich cis elements are deleted, indicating that the protein interacts differently with the D. virilis promoter than it does with the D. melanogaster promoter. Since CLAMP and MSL2 directly interact in D. melanogaster, we propose that D. virilis CLAMP recruits MSL2 to an ectopic autosomal site through interaction with X-like cis elements. Further, localization of MSL2 to one of the D. virilis histone loci suggests that the loci are regulated differently and that males and females have different requirements for histone gene regulation.

genetics↗

bioRxiv2022

A cost-free CURE: Using bioinformatics to identify DNA-binding factors at a specific genomic locus

Research experiences provide diverse benefits for undergraduates. Many academic institutions have adopted course-based undergraduate research experiences (CUREs) to improve student access to research opportunities. However, potential instructors of a CURE might still face financial or practical hurdles that prevent implementation. Bioinformatics research offers an alternative that is free, safe, compatible with remote learning, and may be more accessible for students with disabilities. Here, we describe a bioinformatics CURE that leverages publicly available datasets to discover novel proteins that target an instructor-determined genomic locus of interest. We use the free, user-friendly bioinformatics platform Galaxy to map ChIP-seq datasets to a genome, which removes the computing burden from students. Both faculty and students directly benefit from this CURE, as faculty can perform candidate screens and publish CURE results. Students gain not only basic bioinformatics knowledge, but also transferable skills, including scientific communication, database navigation, and primary literature experience. The CURE is flexible and can be expanded to analyze different types of high-throughput data or to investigate different genomic loci in any species.

scientific communication and education↗