Biology subjects

Marasco, L. E.

Publications and source records attributed to Marasco, L. E..

3 recordsLinked to original sources

bioRxiv2026

Nucleolar endonuclease MBLAC2 orchestrates co-transcriptional ribosomal RNA processing and global transcriptional output

The metallo-{beta}-lactamase (MBL)-domain superfamily includes multiple nucleases that process distinct transcript classes. We show that human MBLAC2 acts as a ribosomal (r)RNA quality control factor, being nucleolar specific, chromatin-associated and required for co-transcriptional pre-rRNA processing. Notably MBLAC2 is functionally distinct from other MBL containing proteins, being required for maintenance of nucleolar architecture, cell cycle progression and proliferative fitness. Selective MBLAC2 depletion causes accumulation of pre-rRNA intermediates that lead to perturbed RNA polymerase (Pol) I-associated RNA homeostasis and nucleolar stress signalling. Nascent RNA profiling with long-read nanopore sequencing reveals extended and aberrant pre-rRNA species, consistent with defective processing and transcript release. Remarkably disruption of rRNA processing reduces global Pol II transcriptional output, even though the Pol II nuclear distribution remains unchanged across genomic compartments. Altogether, we define MBLAC2 as the nucleolar branch of an MBL-domain RNA surveillance network that couples rRNA quality control with transcriptional homeostasis.

molecular biology↗

bioRxiv2025

An SMN2 splicing-correcting antisense oligonucleotide promotes gene looping

We have previously proposed a combined therapy for spinal muscular atrophy based on the upregulation of exon 7 (E7) inclusion into SMN2 mRNA by the antisense oligonucleotide nusinersen (ASO1) together with histone deacetylase inhibitors (HDACi). Using a CRISPR/deadCas-based strategy, we show here that targeting histone acetylation at the SMN2 E7 region duplicates the HDACi effect, which overcomes pleiotropic effects. Most noticeably, targeted acetylation at the E7 region causes acetylation and activation of the 30-kbp-distant promoter. Since E7 and the nusinersen target site map near the SMN2 gene 3'-end, this cross-talk between the two ends of the gene prompted us to use chromosome conformation analysis (3C) to find that ASO1 promotes gene looping. This unpredicted property of ASOs in modulating chromatin 3D configuration depends on cohesin, CTCF, cleavage/polyadenylation factors and a canonical poly(A) signal, and causes promoter activation at a long distance, which expands the therapeutic potential of splicing-correcting ASOs.

molecular biology↗

bioRxiv2021

Towards a combined therapy for spinal muscular atrophy based on opposing effects of an antisense oligonucleotide on chromatin and splicing

Spinal Muscular Atrophy (SMA) is a motor-neuron disease caused by loss-of-function mutations of the SMN1 gene. Humans have a paralog, SMN2, whose exon 7 is predominantly skipped, and so it cannot fully compensate for the lack of SMN1. Nusinersen (Spinraza) is a splicing-correcting antisense oligonucleotide drug (ASO) approved for clinical use. Nusinersen targets a splicing silencer located in SMN2 intron 7 pre-mRNA and, by blocking the binding of the splicing repressors hnRNPA1 and A2, it promotes higher E7 inclusion, increasing SMN protein levels. We show here that, by promoting transcriptional elongation, histone deacetylase (HDAC) inhibitors cooperate with a nusinersen-like ASO to upregulate E7 inclusion. Surprisingly, the ASO also elicits the deployment of the silencing histone mark H3K9me2 on the SMN2 gene, creating a roadblock to RNA polymerase II elongation that acts negatively on E7 inclusion. By removing the roadblock, HDAC inhibition counteracts the undesired chromatin effects of the ASO, resulting in higher E7 inclusion. Combined systemic administration of the nusinersen-like ASO and HDAC inhibitors in neonate SMA mice had strong synergistic effects on SMN expression, growth, survival, and neuromuscular function. Thus, we suggest that HDAC inhibitors have the potential to increase the clinical efficacy of nusinersen, and perhaps other splicing-modulatory ASO drugs, without large pleiotropic effects, as assessed by genome-wide analyses.

molecular biology↗