Biology subjects

Anastasakis, D. G.

Publications and source records attributed to Anastasakis, D. G..

7 recordsLinked to original sources

bioRxiv2026

An ancestral tRNA maturation enzyme repurposed for cytoplasmic non-coding RNA processing

Ribonuclease Z enzymes remove 3' trailers from precursor tRNAs. In human cells, ELAC2/RNase ZL matures nuclear and mitochondrial pre-tRNAs, whereas the cytosolic short paralog ELAC1/RNase ZS repairs ANKZF1-cleaved tRNAs, but its broader substrate repertoire remains unclear. We investigated ELAC1 function using transcriptome profiling, small RNA sequencing, CLIP-seq, and biochemical reconstitution. ELAC1 was dispensable for canonical tRNA processing but associated with structured RNA polymerase III transcripts, prominently Y RNAs and vault RNAs (vtRNAs). Purified ELAC1 cleaved all four human vtRNAs near their 3' ends, with high-resolution mapping identifying a conserved cleavage position within the 3' extension. Efficient cleavage required structural features of the vtRNA terminal region. In contrast, ELAC2 showed little or no vtRNA cleavage under the conditions tested and displayed stricter substrate and cleavage-site selection on pre-tRNA. Loss and re-expression of ELAC1 altered structured ncRNA abundance and small-RNA end profiles. These findings identify vtRNAs as direct ELAC1 substrates and support functional specialization of human ELAC paralogs, with ELAC2 favoring precise pre-tRNA maturation and ELAC1 exhibiting broader RNA substrate specificity.

molecular biology↗

bioRxiv2026

The human DEAD-box protein DDX3X regulates host and viral mRNA translation during Sendai Virus infection

DDX3X is a multifunctional DEAD-box RNA helicase with important roles in translation initiation and antiviral innate immune signaling, yet it is currently unknown whether viral infection affects its interactions with host RNAs. Here, we define the transcriptome-wide binding landscape of endogenous DDX3X in Sendai virus-infected human cells using PAR-CLIP. We show that DDX3X maintains its preference for GC-rich, highly structured 5'UTR regions during infection, but acquires a distinct set of infection-induced targets, including IFNB1 and multiple interferon-stimulated genes. We demonstrate that DDX3X directly binds the IFNB1 5'UTR and promotes its translation, establishing a previously unrecognized post-transcriptional mechanism contributing to DDX3X-dependent IFN-{beta} production. We also evaluated DDX3Xs binding to SeV RNAs and concluded that DDX3X is likely not actively recruited by SeV or has a significant effect on its viral life cycle. Our findings add a novel dimension to DDX3Xs involvement in anti-viral immunity with implications for further therapeutic development of DDX3X inhibitors.

molecular biology↗

bioRxiv2025

RBProximity-CLIP Enables Subcellular Mapping of RNA-Binding Protein Interactions at Nucleotide Resolution

RNA-binding proteins (RBPs) enable post-transcriptional gene regulation (PTGR) through specific interactions with RNA molecules, influencing processes ranging from nuclear processing and export to cytoplasmic localization, translation, storage and degradation. A key determinant of PTGR processes is the subcellular compartmentalization of RBPs, which dictates RNA targets they can access and the regulation performed in that environment. To characterize RBP-RNA interactions at subcellular resolution, we developed RBProximity-CLIP. RBProximity-CLIP enables compartment-specific isolation and profiling of individual RBP-RNA interactions by combining APEX2-based proximity labeling and 4-thiouridine-enhanced RNA-protein crosslinking, with sequential RBP- and biotin-affinity purifications. Using this approach, we profiled the RNA targets of three RBPs, AGO2, YBX1, and ELAVL1, across the cytoplasmic, nuclear, and nucleolar compartments, revealing nucleus-specific miRNA-mediated AGO2 targets, as well as subsets of YBX1 and ELAVL1 targets that differ by compartment, yet share identical binding motifs. RBProximity-CLIP enables specific and sensitive detection of compartment-specific RBP-RNA interactomes, thereby providing new insight into spatial gene regulation by RBPs.

cell biology↗

bioRxiv2025

The MLLT3 YEATS domain is a dual reader of histone marks (H3K9/18/27ac/cr) and ncRNA (7SK), linking epigenetic and RNA signaling to regulate hematopoiesis

The protein MLLT3 (AF9) is a critical regulator of hematopoiesis. The N-terminal YEATS domain of MLLT3 is an epigenetic reader that binds to acetylated as well as crotonylated lysine. Using PAR-CLIP, biochemical assays, and NMR based mapping of binding, we demonstrate that the YEATS domain of MLLT3 binds to a specific stem-loop region of the noncoding RNA 7SK. 7SK is a noncoding RNA with a well-documented function in transcriptional elongation. We developed point mutations in the YEATS domain that disrupt RNA binding while having no effect on binding of acetylated histone peptides to probe the specific role of RNA binding in MLLT3 function. Our results show loss of RNA binding by MLLT3 skews hematopoietic differentiation away from the myeloid lineage and toward the lymphoid lineage and has substantial effects on gene expression, confirming the essential nature of MLLT3-RNA binding for function.

biochemistry↗

bioRxiv2024

Nuclear RNAi Modulates Influenza A Virus Infectivity By Downregulating Type-I Interferon Response

The role of Argonaute (AGO) proteins and the RNA interference (RNAi) machinery in mammalian antiviral response has been debated. Therefore, we set out to investigate how mammalian RNAi impacts influenza A virus (IAV) infection. We reveal that IAV infection triggers nuclear accumulation of AGO2, which is directly facilitated by p53 activation. Mechanistically, we show that IAV induces nuclear AGO2 targeting of TRIM71, a proposed AGO2 E3 ligase, and type-I interferon-pathway genes for silencing. Accordingly, Tp53-/- mice do not accumulate nuclear AGO2 and demonstrate decreased susceptibility to IAV infection. Hence, the RNAi machinery is highjacked by the virus to evade the immune system and support viral replication. Furthermore, the FDA approved drug arsenic trioxide, which prevents p53 tetramerization and nuclear translocation, increases interferon response and decreases viral replication in vitro and in a mouse model in vivo. Our data indicates that targeting the AGO2:p53-mediated silencing of innate immunity may offer a promising strategy to mitigate viral infections.

biochemistry↗

bioRxiv2022

Matrin3 regulates cell proliferation and spindle dynamics by regulating CDC14B alternative splicing

Matrin3 is an RNA-binding protein that affects diverse RNA-related processes, including mRNA splicing. While Matrin3 has been intensively studied in neurodegenerative diseases, its function in cancer remains unclear. Here, we discovered Matrin3-mediated regulation of mitotic spindle dynamics in colorectal cancer (CRC) cells. We identified bound and regulated Matrin3-target RNAs transcriptome-wide in CRC cells and found that Matrin3 broadly modulates mRNA splicing patterns. Among the top Matrin3 targets, we focused on CDC14B and found that Matrin3 loss increased inclusion of an exon containing a premature termination codon into the CDC14B transcript and simultaneous down-regulation of the standard CDC14B transcript. Selective knockdown of the CDC14B standard transcript phenocopied Matrin3 knockdown and exhibited reduced proliferation and defects in mitotic spindle formation, suggesting that CDC14B is a key downstream effector of Matrin3. Collectively, these data reveal an important role for the Matrin3/CDC14B axis in control of CRC cell proliferation and mitotic spindle formation.

molecular biology↗

bioRxiv2020

Multiple Capsid Protein Binding Sites Mediate Selective Packaging of the Alphavirus Genomic RNA

The alphavirus capsid protein (Cp) selectively packages genomic RNA (gRNA) into the viral nucleocapsid to produce infectious virus. Using photoactivatable ribonucleoside crosslinking and an innovative biotinylated Cp retrieval method, we comprehensively defined binding sites for Semliki Forest virus (SFV) Cp on the gRNA. While data in infected cells demonstrated Cp binding to the proposed genome packaging signal (PS), mutagenesis experiments showed that PS was not required for production of infectious SFV or Chikungunya virus. Instead, we identified multiple novel Cp binding sites that were enriched on gRNA-specific regions and promoted infectious SFV production and gRNA packaging. Comparisons of binding sites in cytoplasmic vs. viral nucleocapsids demonstrated that budding caused discrete changes in Cp-gRNA interactions. Notably, Cps top binding site was maintained throughout virus assembly, and specifically bound and assembled with Cp into core-like particles in vitro. Together our data suggest a new model for selective alphavirus genome recognition and assembly.

microbiology↗