Biology subjects

Bloom, K. S.

Publications and source records attributed to Bloom, K. S..

3 recordsLinked to original sources

bioRxiv2025

HP1-enhanced chromatin compaction stabilizes a synthetic metabolic circuit in yeast

Chromatin compaction defines genome topology, evolution, and function. The Saccharomycotina subphylum, including the fermenting yeast Saccharomyces cerevisiae have a decompacted genome, possibly because they lost two genes mediating a specific histone lysine methylation and histone binding protein heterochromatin protein 1 (HP1). This decompaction may result in the higher-than-expected mutation and meiotic recombination rates observed in this species. To test this hypothesis, we retro-engineered S. cerevisiae to compact the genome by expressing the HP1 homologue of Schizosaccharomyces pombe SpSwi6 and H3K9 methyltransferase SpClr4. The resulting strain had significantly more compact chromatin and reduced rates of mutation and meiotic recombination. The increased genomic stability significantly prolongs the optogenetic control of an engineered strain designed to grow only in blue light. This result demonstrates the potential of our approach to enhance the stability of strains for metabolic engineering and other synthetic biology applications, which are prone to lose activities due to genetic instability.

synthetic biology↗

bioRxiv2023

A bacterial expression cloning screen reveals tardigrade single-stranded DNA-binding proteins as potent desicco-protectants

Tardigrades are known for their ability to survive remarkable extremes, but relatively little is known about the molecular underpinnings that allow for their extraordinary stress tolerance. We devised an expression cloning approach to screen for novel protectants from desiccation-tolerant tardigrades. We expressed cDNA libraries from the tardigrades Hypsibius exemplaris and Ramazzottius varieornatus in E. coli and subjected the bacteria to desiccation. Sequencing the populations of surviving bacteria revealed enrichment of mitochondrial single-stranded DNA-binding proteins (mtSSBs) from both tardigrade species. Expression of mtSSBs in bacteria improved desiccation survival to similar levels as some of the best protectants known to date. The DNA-binding activity of the oligonucleotide/oligosaccharide binding (OB) fold domain of mtSSB was necessary and sufficient to improve desiccation tolerance. By comparing the efficacy of mtSSBs from multiple organisms, we provide evidence that desicco-protection is a conserved feature of mtSSBs. More broadly, any OB-fold containing protein may act similarly to promote desiccation tolerance, likely by coating ssDNA to limit damage during desiccation. These results identify single-stranded DNA-binding activity as a potent contributor to extreme desiccation tolerance.

molecular biology↗

bioRxiv2018

Transfer RNA Genes Affect Chromosome Structure and Function via Local Effects

The genome is packaged and organized in an ordered, non-random manner and specific chromatin segments contact nuclear substructures to mediate this organization. While transfer RNA genes (tDNAs) are essential for the generation of tRNAs, these loci are also binding sites for transcription factors and architectural proteins and are thought to play an important role in the organization of the genome. In this study, we investigate the role of tDNAs in genomic organization and chromosome function by editing a chromosome so that it lacks any tDNAs. Surprisingly our analyses of this tDNA-less chromosome show that loss of tDNAs does not grossly affect chromosome folding or chromosome tethering. However, loss of tDNAs affects local nucleosome positioning and the binding of SMC proteins at these loci. The absence of tDNAs also leads to changes in centromere clustering and a reduction in the frequency of long range HML-HMR heterochromatin clustering. We propose that the tDNAs primarily affect local chromatin structure that result in effects on long-range chromosome architecture.

molecular biology↗