Biology subjects

Hronova, V.

Publications and source records attributed to Hronova, V..

3 recordsLinked to original sources

bioRxiv2023

Stem-loop induced ribosome queuing in the uORF2/ATF4 overlap fine-tunes stress-induced human ATF4 translational control

ATF4 is a master transcriptional regulator of the integrated stress response leading cells towards adaptation or death. ATF4s induction under stress was thought to be mostly due to delayed translation reinitiation, where the reinitiation-permissive uORF1 plays a key role. Accumulating evidence challenging this mechanism as the sole source of ATF4 translation control prompted us to investigate additional regulatory routes. We identified a highly conserved stem-loop in the uORF2/ATF4 overlap, immediately preceded by a near-cognate CUG, which introduces another layer of regulation in the form of ribosome queuing. These elements explain how the inhibitory uORF2 can be translated under stress, confirming prior observations, but contradicting the original regulatory model. We also identified two highly conserved, potentially modified adenines performing antagonistic roles. Finally, we demonstrate that the canonical ATF4 translation start site is substantially leaky-scanned. Thus, ATF4s translational control is more complex than originally described underpinning its key role in diverse biological processes.

molecular biology↗

bioRxiv2021

Regulatory start-stop elements in 5' untranslated regions pervasively modulate translation

Sequence elements within the 5 untranslated region (UTR) of eukaryotic genes, e.g. upstream open reading frames (uORFs), control translation of eukaryotic genes. We describe an element consisting of a start codon immediately followed by a stop codon which is distinct from uORFs in the lack of an elongation step. Start-stops have been described for specific cases, but their widespread impact has been overlooked. Start-stop elements occur in the 5UTR of 1, 417 human genes and are more often occupied with a ribosome than canonical uORFs or control sequences. Start-stops efficiently halt ribosomes without evidence for accelerated RNA turnover, therefore acting as a barrier for the scanning of the small ribosomal subunit and repressing downstream translation. Our results suggest a model by which the ribosome undergoes repeated cycles of termination and partial ribosomal recycling, during which the large subunit detaches, but the 40S subunit with the Met-tRNAiMet remains associated with the mRNA to be rejoined by the 60S subunit. Start-stop elements occur in many transcription factors and signaling genes, and affect cellular fate via different routes. We investigate the start-stop element in several genes, i.e. MORF4L1, SLC39A1, and PSPC1, and in more detail in ATF4.

systems biology↗

bioRxiv2019

Selective Translation Complex Profiling Reveals Staged Initiation and Co-translational Assembly of Initiation Factor Complexes

Translational control targeting mainly the initiation phase is central to the regulation of gene expression. Understanding all of its aspects requires substantial technological advancements. Here we modified yeast Translational Complex Profile sequencing (TCP-seq), related to ribosome profiling, and adopted it for mammalian cells. Human TCP-seq, capable of capturing footprints of 40S subunits (40Ses) in addition to 80S ribosomes (80Ses), revealed that mammalian and yeast 40Ses distribute similarly across 5UTRs indicating considerable evolutionary conservation. We further developed a variation called Selective TCP-seq (Sel-TCP-seq) enabling selection for 40Ses and 80Ses associated with an immuno-targeted factor in yeast and human. Sel-TCP-seq demonstrated that eIF2 and eIF3 travel along 5UTRs with scanning 40Ses to successively dissociate upon start codon recognition. Manifesting the Sel-TCP-seq versatility for gene expression studies, we also identified four initiating 48S conformational intermediates, provided novel insights into ATF4 and GCN4 mRNA translational control, and demonstrated co-translational assembly of initiation factor complexes.

molecular biology↗