Biology subjects

Alecki, C.

Publications and source records attributed to Alecki, C..

3 recordsLinked to original sources

bioRxiv2023

Localized synthesis of molecular chaperones sustains neuronal proteostasis

Proteostasis is maintained through regulated protein synthesis and degradation and chaperone-assisted protein folding. However, this is challenging in neuronal projections because of their polarized morphology and constant synaptic proteome remodeling. Using high-resolution fluorescence microscopy, we discovered that hippocampal and spinal cord motor neurons of mouse and human origin localize a subset of chaperone mRNAs to their dendrites and use microtubule-based transport to increase this asymmetric localization following proteotoxic stress. The most abundant dendritic chaperone mRNA encodes a constitutive heat shock protein 70 family member (HSPA8). Proteotoxic stress also enhanced HSPA8 mRNA translation efficiency in dendrites. Stress-mediated HSPA8 mRNA localization to the dendrites was impaired by depleting fused in sarcoma--an amyotrophic lateral sclerosis-related protein--in cultured spinal cord mouse motor neurons or by expressing a pathogenic variant of heterogenous nuclear ribonucleoprotein A2/B1 in neurons derived from human induced pluripotent stem cells. These results reveal a crucial and unexpected neuronal stress response in which RNA-binding proteins increase the dendritic localization of HSPA8 mRNA to maintain proteostasis and prevent neurodegeneration.

molecular biology↗

bioRxiv2022

The ribosome quality control factors Asc1 and Hel2 regulate the expression of HSP70 during heat shock and recovery

Cells rapidly adapt to survive harsh environmental conditions through the potent upregulation of molecular chaperones or heat shock proteins (HSPs). The inducible members of the HSP70 family are the fastest and most transcriptionally induced chaperone upon stress. The HSP70 mRNA life cycle regulation in the cytoplasm is unique because it is translated during stress when general translation is repressed and rapidly degraded once conditions are optimal for growth. Contrary to the role of the HSP70 mRNA 5 untranslated region in maximizing the synthesis of HSP70, we discovered that the coding sequence (CDS) represses its translation through the ribosome quality control (RQC) mechanism. The CDS of the most inducible HSP70 in Saccharomyces cerevisiae, SSA4, is uniquely biased with low-frequency codons that promote ribosome stalling during heat stress. The stalled ribosomes are recognized by RQC components Asc1p and Hel2p and two ribosome proteins, Rps28A and Rps19B, that we identified as new RQC components. Surprisingly, RQC does not signal the degradation of the SSA4 mRNA by no-go-decay (NGD). Instead, Asc1p destabilizes the SSA4 mRNA during recovery from heat stress by a mechanism independent of its ribosome binding and SSA4 CDS codon optimality. Therefore, Asc1p operates two synergistic mechanisms that converge to regulate the life cycle of HSP70 mRNA during stress and recovery. Our research identifies Asc1p as a critical regulator of the stress response and RQC as the system tuning HSP70 synthesis.

molecular biology↗

bioRxiv2019

RNA strand invasion activity of the Polycomb complex PRC2

Epigenetic regulation is conveyed through information encoded by specific chromatin features. Non-canonical nucleic acid structures could in principle also convey biological information but their role(s) in epigenetic regulation is not known. Polycomb Group (PcG) proteins form memory of transient transcriptional repression events that is necessary for development. In Drosophila, PcG proteins are recruited to specific DNA sequences, Polycomb Response Elements (PREs). PREs are switchable memory elements that can exist in repressed, active, or unengaged states 1,2. How PcG activities are targeted to PREs to maintain repressed states only in appropriate developmental contexts has been difficult to elucidate. Biochemically, PcG protein complexes modify chromatin to maintain gene repression 1,3,4. However, PcG proteins also interact with both RNA and DNA, and RNA is implicated in the targeting of PcG function. We find that R-loops, three-stranded nucleic acid structures formed when an RNA hybridizes to its complementary DNA and displaces the other DNA strand 5, form at many PREs in Drosophila embryos, and correlate with the repressive state. R-loops are recognized by the PcG complex PRC1 in vitro. Unexpectedly, we find that the PcG complex PRC2 has RNA strand invasion activity, which can drive formation of RNA-DNA hybrids, the key component of R-loops. Our results suggest a new mechanism for targeting PcG function through R-loop formation by PRC2 and recognition by PRC1. More generally, our findings suggest formation and recognition 6 of non-canonical nucleic acid structures as an epigenetic mechanism.

biochemistry↗