Biology subjects

Lin, D. H.

Publications and source records attributed to Lin, D. H..

4 recordsLinked to original sources

bioRxiv2026

The E3 ubiquitin ligase mechanism specifying target-directed microRNA degradation

MicroRNAs (miRNAs) associate with Argonaute (AGO) proteins to form complexes that down-regulate target RNAs, including mRNAs from most human genes1-3. Within each complex, the miRNA pairs to target mRNAs to specify their repression, and AGO provides effector function while also protecting the miRNA from cellular nucleases2-5. Although much has been learned about this mode of posttranscriptional gene regulation, less is known about how the miRNAs themselves are regulated. In one such regulatory pathway, unusual miRNA targets called "trigger" RNAs reverse the canonical regulatory logic and instead down-regulate microRNAs6-21. This target-directed miRNA degradation (TDMD) is thought to require a cullin-RING E3 ligase (CRL) because it depends on the cullin protein CUL3 and other ubiquitylation components, including the BC-box protein ZSWIM8 (ref. 22,23). ZSWIM8 is required for murine perinatal viability and for destabilization of most short-lived miRNAs, but is otherwise poorly understood23-25. Here, we demonstrate that a human AGO-miRNA- trigger complex selectively binds ZSWIM8 for CUL3-mediated polyubiquitylation of the AGO protein within this complex. Cryogenic electron-microscopy (cryo-EM) analyses show how ZSWIM8 recognizes the distinct AGO2 and miRNA-trigger conformations shaped by pairing of the miRNA to the trigger. For example, this pairing extracts the miRNA from a binding pocket within AGO2, allowing the pocket to be captured by ZSWIM8, and it directs the trigger RNA along a distinct trajectory to be also recognized by ZSWIM8. These results biochemically establish AGO binding and polyubiquitylation as the key regulatory step of TDMD, define a unique CRL class, and reveal generalizable RNA-RNA, RNA-protein, and protein-protein interactions that specify the ubiquitin-mediated degradation of AGO with exquisite selectivity. The substrate features recognized by the E3 ubiquitin ligase do not conform to a conventional degron26-28, but rather establish a two-RNA-factor authentication mechanism specifying a protein ubiquitylation substrate.

biochemistry↗

bioRxiv2025

mRNA 3' UTRs direct microRNA degradation to participate in imprinted gene networks and regulate growth

MicroRNAs direct downregulation of target mRNAs. Sometimes, however, this regulatory paradigm inverts, and a target RNA triggers the degradation of a microRNA. This target-directed microRNA degradation (TDMD) requires ZSWIM8. Zswim8-/- mice exhibit reduced growth and perinatal lethality, accompanied by stabilization of dozens of microRNAs. Nonetheless, studies of TDMD function in mammals have been limited because only two TDMD-triggering RNAs have been identified in mice. Here, we computationally identify and validate five new TDMD-triggering sites in mouse models. One site in Atp6v1g1 and two in Lpar4 direct degradation of miR-335-3p, which shows that in mammals, two sites in the same transcript, and multiple sites in different transcripts, can collaborate to destabilize a microRNA. Moreover, sites in Plagl1 and Lrrc58 direct degradation of miR-322 and miR-503, respectively. Mice lacking the Plagl1 and Lrrc58 sites exhibit reduced growth, demonstrating that target-directed degradation of miR-503 and miR-322 promotes mammalian growth. Both miR-335-3p and Plagl1 are maternally imprinted, implying that they participate in parental conflict, but their corresponding triggers or target microRNA partner are not imprinted. Thus, 3' UTRs directly participate in parental conflict by engaging TDMD to access an additional layer of regulation within a network of imprinted and biallelic genes.

molecular biology↗

bioRxiv2025

Lysosomal RNA profiling reveals targeting of specific types of RNAs for degradation

Autophagy targets a wide variety of substrates for degradation within lysosomes1. While lysosomes are known to possess RNase activity2, the role of lysosomal RNA degradation in post-transcriptional gene regulation is not well understood. Here, we define RNASET2, PLD3, and both endogenous and exogenous RNase A family members as lysosomal RNases. Cells lacking these RNases accumulated large amounts of lysosomal RNA. Although all types of RNA can be found within lysosomes, SRP RNAs, Y RNAs, 5' TOP mRNAs, long-lived mRNAs, and mRNAs encoding membrane and secreted proteins were specifically enriched. All types of RNA depend on autophagy for lysosomal targeting, but the lysosomally-enriched RNAs are more sensitive to loss of autophagy, implying that selective mechanisms mediate their lysosomal entry. RNA stability measurements revealed that lysosomally-degraded transcripts also had autophagy-dependent changes in stability. In exploring how specific RNAs are targeted for lysosomal degradation, we found that the Alu domain of SRP RNAs is sufficient for targeting these RNAs to lysosomes in fashion that depends on its interactions with the SRP9 and SRP14 proteins. For mRNAs, 5' TOP motifs are sufficient to increase their targeting to lysosomes for degradation in a LARP1-dependent manner. Altogether, our results establish lysosomes as selective modulators of cellular RNA content.

molecular biology↗

bioRxiv2021

Architecture of the cytoplasmic face of the nuclear pore

The nuclear pore complex (NPC) is the sole bidirectional gateway for nucleocytoplasmic transport. Despite recent progress in elucidating the NPC symmetric core architecture, the asymmetrically decorated cytoplasmic face, essential for mRNA export and a hotspot for nucleoporin-associated diseases, has remained elusive. Here, we report a composite structure of the entire human cytoplasmic face obtained by combining biochemical reconstitution, crystal structure determination, docking into cryo-electron tomographic reconstructions, and physiological validation, accounting for a third of the NPCs mass. Whereas an evolutionarily conserved [~]540 kDa hetero-hexameric cytoplasmic filament nucleoporin complex is anchored by species-specific motifs above the central transport channel, attachment of the pentameric NUP358 bundles depends on the double-ring arrangement of the coat nucleoporin complex. Our results and the predictive power of our composite structure provide a rich foundation for elucidating the molecular basis of mRNA export and nucleoporin diseases. One sentence summaryAn interdisciplinary analysis established the near-atomic molecular architecture of the cytoplasmic face of the human nuclear pore complex.

biochemistry↗