Biology subjects

Sgromo, A.

Publications and source records attributed to Sgromo, A..

3 recordsLinked to original sources

bioRxiv2026

A pseudohelicase-centered complex couples assembly-dependent RNA cleavage to poly(UG)ylation

Robust RNA interference in Caenorhabditis elegans requires Argonaute targeted RNAs to be cleaved by RDE 8 and poly(UG)ylated by MUT 2, generating templates for RNA dependent RNA polymerases that synthesize secondary small RNAs. RDE 8 and MUT 2 are physically coupled within the cleavage and poly(UG)ylation (CPUG) complex, together with the pseudonuclease NYN 1 and MUT 15, but how their activities are controlled and coordinated is unknown. Structural and biochemical analyses reveal that the RDE 8/NYN 1 nuclease module is autoinhibited, restricting cleavage outside CPUG. We identify MUT 15, the CPUG scaffold linking this nuclease module to MUT 2, as a pseudohelicase. MUT 15 remodels the nuclease module, licensing RDE 8 activity upon complex assembly. Reconstituted CPUG synthesizes long poly(UG) tails, with the substrate 3' end determining tailing efficiency and register. Within CPUG, RNA engagement by MUT 2 limits RDE 8 access, while poly(UG) tails themselves are not cleaved by RDE 8, preventing re cleavage. Together, CPUG couples assembly dependent RNA cleavage to downstream processing, imposing safety and directionality.

biochemistry↗

bioRxiv2026

Kinetic logic of uridylation-mediated RNA decay

3'-terminal uridylation marks structured non-coding RNAs for cytoplasmic decay, yet how uridylation is quantitatively coupled to exonucleolytic degradation remains unclear. Here, we dissect the kinetic logic of uridylation-mediated RNA surveillance in Drosophila melanogaster. Using biochemical reconstitution together with high-throughput enzymology and quantitative modeling, we show that the terminal uridylyl transferase Tailor generates discrete oligo(U) intermediates through product-dependent kinetic tuning, while co-substrate promiscuity suppresses sustained processivity under physiological nucleotide conditions. Massively parallel binding and decay assays further reveal how the 3'-to-5' exoribonuclease Dis3l2 selectively degrades Tailor-primed RNAs by integrating 3'-proximal uridine content and defined 3'-end accessibility--features encoded by short, kinetically tuned oligo(U) intermediates centered on four nucleotides--to enable productive threading of RNA substrates along an extended RNA-binding path to the catalytic site. Together, our findings establish a quantitative framework in which uridylation encodes decay competence through transient RNA 3'-end states that are matched to the mechanistic requirements for decay. HighlightsO_LIThe TUTase Tailor kinetically tunes uridylation to generate short, discrete oligo(U) intermediates C_LIO_LIMixed nucleotide availability suppresses sustained processive uridylation C_LIO_LIDis3l2 decodes 3'-proximal uridine content and end accessibility to commit RNAs to decay C_LIO_LIShort oligo(U) tails encode RNA decay competence through transient RNA 3'-end states C_LI

biochemistry↗

bioRxiv2021

Rapid gene evolution in an ancient post-transcriptional and translationalregulatory system compensates for meiotic X chromosomal inactivation

It is conventionally assumed that conserved pathways evolve slowly with little participation of gene evolution. Nevertheless, it has been recently observed that young genes can take over fundamental functions in essential biological processes, for example, development and reproduction. It is unclear how newly duplicated genes are integrated into ancestral networks and reshape the conserved pathways of important functions. Here, we investigated origination and function of two autosomal genes that evolved recently in Drosophila: Poseidon and Zeus, which were created by RNA-based duplications from the X-linked CAF40, a subunit of the conserved CCR4-NOT deadenylase complex involved in post-transcriptional and translational regulation. Knockdown and knockout assays show that the two genes quickly evolved critically important functions in viability and male fertility. Moreover, our transcriptome analysis demonstrates that the three genes have a broad and distinct effect in the expression of hundreds of genes, with almost half of the differentially expressed genes being perturbed exclusively by one paralog, but not the others. Co-immunoprecipitation and tethering assays show that the CAF40 paralog Poseidon maintains the ability to interact with the CCR4-NOT deadenylase complex and might act in post-transcriptional mRNA regulation. The rapid gene evolution in the ancient post-transcriptional and translational regulatory system may be driven by evolution of sex chromosomes to compensate for the meiotic X chromosomal inactivation (MXCI) in Drosophila.

evolutionary biology↗