Biology subjects

Williams, R. T.

Publications and source records attributed to Williams, R. T..

3 recordsLinked to original sources

bioRxiv2022

Translation of the ERM-1 membrane-binding domain directs erm-1 mRNA localization to the plasma membrane in the C. elegans embryo

mRNA localization and transport are integral in regulating gene expression. In Caenorhabditis elegans embryos, the maternally inherited mRNA erm-1 (Ezrin/Radixin/Moesin) concentrates in anterior blastomeres. erm-1 mRNA localizes within those blastomeres to the plasma membrane where the essential ERM-1 protein, a membrane-actin linker, is also found. We demonstrate that the localization of erm-1 mRNA to the plasma membrane is translation-dependent and requires its encoded N-terminal membrane-binding (FERM) domain. By perturbing translation through multiple methods, we found erm-1 mRNA localization at the plasma membrane was maintained only if the nascent peptide remained in complex with the translating mRNA. Indeed, recoding the erm-1 mRNA coding sequence while preserving the encoded amino acid sequence did not disrupt erm-1 mRNA localization, corroborating that the information directing mRNA localization resides within its membrane-binding protein domain. A smiFISH screen of 17 genes encoding similar membrane-binding domains identified three plasma membrane localized mRNAs in the early embryo. Nine additional transcripts showed apparent membrane localization later in development. These findings point to a translation-dependent pathway for localization of mRNAs encoding membrane-associated proteins. SUMMARY STATEMENTIn C. elegans, erm-1 mRNA localization to plasma membranes requires translation of the ERM-1 membrane-binding domain

developmental biology↗

bioRxiv2021

The transcription factor ELT-2 positively and negatively impacts direct target genes to modulate the Caenorhabditis elegans intestinal transcriptome

ELT-2 is the major transcription factor required for Caenorhabditis elegans intestinal development. ELT-2 expression initiates in embryos to promote development and then persists after hatching through the larval and adult stages. Though the sites of ELT-2 binding are characterized and the transcriptional changes that result from ELT-2 depletion are known, an intestine-specific transcriptome profile spanning developmental time has been missing. We generated this dataset by performing Fluorescence Activated Cell Sorting (FACS) on intestine cells at distinct developmental stages. We analyzed this dataset in conjunction with previously conducted ELT-2 studies to evaluate the role of ELT-2 in directing the intestinal gene regulatory network through development. We found that only 33% of intestine-enriched genes in the embryo were direct targets of ELT-2 but that number increased to 75% by the L3 stage. This suggests additional transcription factors promote intestinal transcription especially in the embryo. Furthermore, only half of ELT-2s direct target genes were dependent on ELT-2 for their proper expression levels, and an equal proportion of those responded to elt-2 depletion with over-expression as with under-expression. That is, ELT-2 can either activate or repress direct target genes. Additionally, we observed that ELT-2 repressed its own promoter, implicating new models for its autoregulation. Together, our results illustrate that ELT-2 impacts roughly 20 - 50% of intestine-specific genes, that ELT-2 both positively and negatively controls its direct targets, and that the current model of the intestinal regulatory network is incomplete as the factors responsible for directing the expression of many intestinal genes remain unknown.

genomics↗

bioRxiv2021

Adaptive stimulation of macropinocytosis overcomes aspartate limitation in cancer cells under hypoxia

Stress-adaptive mechanisms enable tumor cells to overcome metabolic constraints in nutrient and oxygen poor tumors. Aspartate is an endogenous metabolic limitation under hypoxic conditions, but the nature of the adaptive mechanisms that contribute to aspartate availability and hypoxic tumor growth are poorly understood. Here, using a combination of metabolomics and CRISPR-based genetic screens, we identify GOT2-catalyzed mitochondrial aspartate synthesis as an essential metabolic dependency for the proliferation of pancreatic tumor cells under hypoxic culture conditions. In contrast, GOT2-catalyzed aspartate synthesis is dispensable for pancreatic tumor formation in vivo. The dependence of pancreatic tumor cells on aspartate synthesis is bypassed in part by a hypoxia-induced potentiation of extracellular protein scavenging via macropinocytosis. This effect is mutant KRas-dependent, and is mediated by hypoxia inducible factor 1 (HIF1A) and its canonical target carbonic anhydrase-9 (CA9) through the cooption of the bicarbonate-macropinocytosis signaling axis. Our findings reveal high plasticity of aspartate metabolism and define an adaptive regulatory role for macropinocytosis by which mutant KRas tumors can overcome nutrient deprivation under hypoxic conditions.

cancer biology↗