Biology subjects

Matunis, M. J.

Publications and source records attributed to Matunis, M. J..

3 recordsLinked to original sources

bioRxiv2025

SUMO2 Promotes Histone Pre-mRNA Processing by Stabilizing Histone Locus Body Interactions and Facilitating U7 snRNP Assembly

Histone mRNAs are the only non-polyadenylated mRNAs in eukaryotic cells and require specialized processing in the histone locus body (HLB), a nuclear body where essential processing factors, including the U7 snRNP, are concentrated. Recent studies have revealed that misregulation of histone pre-mRNA processing can lead to polyadenylation of histone mRNAs and disruption of histone protein homeostasis. Despite links to human disease, the factors contributing to polyadenylation of histone mRNAs and the mechanisms underlying HLB assembly and U7 snRNP biogenesis remain unclear. Here, we report novel functions of the small ubiquitin-related modifier 2 (SUMO2) in promoting histone pre-mRNA processing. Using a SUMO2 knockout osteosarcoma cell line, we identified a defect in 3 end cleavage and a global increase in histone mRNA polyadenylation. Subsequent analysis of HLBs revealed increased dynamics and reduced levels of the U7 snRNP complex. By over-expressing U7 snRNP-specific components, Lsm11 and U7 snRNA, we rescued U7 snRNP levels and processing defects in SUMO2 knockout cells. Through analysis of Lsm11, we identified a SUMO-interacting motif in its N-terminus required for efficient formation of U7 snRNP. Collectively, we demonstrate that SUMO2 promotes histone pre-mRNA 3 end processing by stabilizing HLB interactions and facilitating U7 snRNP assembly.

molecular biology↗

bioRxiv2025

Telomeric SUMO level influences the choices of APB formation pathways and ALT efficiency

Many cancers use an alternative lengthening of telomeres (ALT) pathway for telomere maintenance. ALT telomeric DNA synthesis occurs in ALT telomere-associated PML bodies (APBs). However, the mechanisms by which APBs form are not well understood. Here, we monitored the formation of APBs with time-lapse imaging employing CRISPR knock-in to track the promyelocytic leukemia (PML) protein at endogenous levels. We found APBs form via two pathways: telomeres recruit PML proteins to nucleate PML bodies de novo, or telomeres fuse with preformed PML bodies. Both nucleation and fusion of APBs require interactions between SUMO and SUMO interaction motifs (SIMs). Moreover, APB nucleation is associated with higher levels of SUMOs and SUMO-mediated recruitment of DNA helicase BLM, resulting in more robust telomeric DNA synthesis. Finally, further boosting SUMO levels at telomeres enhances APB nucleation, BLM enrichment, and telomeric DNA synthesis. Thus, high SUMO levels at telomeres promote APB formation via nucleation, resulting in stronger ALT activity.

cell biology↗

bioRxiv2020

Keratin 17 regulates nuclear morphology and chromatin organization

Keratin 17 (KRT17; K17), a non-lamin intermediate filament protein, was recently found to occur in the nucleus. We report here on K17-dependent differences in nuclear morphology, chromatin organization, and cell proliferation. Human tumor keratinocyte cell lines lacking K17 exhibit flatter nuclei relative to normal. Re-expression of wildtype K17, but not a mutant form lacking an intact nuclear localization signal (NLS), rescues nuclear morphology in KRT17 null cells. Analyses of primary cultures of skin keratinocytes from a mouse strain expressing K17 with a mutated NLS corroborated these findings. Proteomics screens identified K17-interacting nuclear proteins with known roles in gene expression, chromatin organization, and RNA processing. Key histone modifications and LAP2{beta} localization within the nucleus are altered in the absence of K17, correlating with decreased cell proliferation and suppression of GLI1 target genes. Nuclear K17 thus impacts nuclear morphology with an associated impact on chromatin organization, gene expression, and proliferation in epithelial cells. SummaryKeratin 17 (K17) is one of two non-lamin intermediate filament proteins recently identified to localize to and function in the cell nucleus. K17 is here shown to regulate nuclear morphology, chromatin organization, LAP2 localization, and cell proliferation.

cell biology↗