Biology subjects

Campos, E. I.

Publications and source records attributed to Campos, E. I..

4 recordsLinked to original sources

bioRxiv2026

PRMT1 arginine methylation of MCM4 restricts ssDNA gap formation during DNA replication

Replication-associated single-stranded DNA (ssDNA) gaps are increasingly recognized as major sources of genome instability, but how replisome-associated mechanisms suppress their formation remains unclear. Here we identify protein arginine methyltransferase 1 (PRMT1) as a replisome-associated methyltransferase that promotes DNA synthesis and fork integrity. PRMT1 localizes to active forks and its depletion or inhibition slows fork progression in multiple human cell types. We identify MCM4 as a direct PRMT1 substrate and show that methylation-deficient MCM4 causes spontaneous replication stress, elevated RPA, and nuclease-sensitive nascent DNA tracts, indicating persistent daughter-strand gaps. Despite these defects, methylation-deficient MCM4 cells exhibit apparent fork acceleration, consistent with discontinuous DNA synthesis. By contrast, PRMT1 depletion slows forks and selectively reduces fork association of SMC5/6 without broadly disrupting core replisome components. Together, these data support a model in which PRMT1-dependent methylation of MCM4 suppresses gap-prone DNA synthesis, while fork-associated SMC5/6 stabilizes vulnerable gap-containing intermediates.

molecular biology↗

bioRxiv2026

ZNF121 recruits YTHDF2 to modulate mRNA stability

N6-methyladenosine (m6A) is the most abundant internal modification in mRNA and has been shown to regulate gene expression through the binding of specific reader proteins, such as YTHDF2, which promotes mRNA decay. Previous studies indicate that YTHDF2 has relatively weak intrinsic RNA-binding affinity, suggesting that additional factors may facilitate its association with target transcripts. Here, we show that the C2H2-Zinc Finger protein, ZNF121, binds mRNA in cells and physically interacts with YTHDF2 in the cytoplasm. We demonstrate that approximately 80% of ZNF121-bound mRNAs are also YTHDF2 targets, and that their binding sites highly correlate with each other. Loss of ZNF121 impairs YTHDF2 binding to shared targets and increases their stability, independent of the presence of m6A modifications. Moreover, co-regulated transcripts are enriched for cell-cycle-related pathways, and ZNF121 depletion leads to elevated expression of the oncogene MDM2, implicating ZNF121 in growth control and the DNA damage response. Our findings identify ZNF121 as a cofactor that enhances YTHDF2-mediated mRNA regulation and reveal a previously unknown layer of control in mRNA decay.

molecular biology↗

bioRxiv2025

H3.3 De Novo Mutations Alter Lysine 36 Methylation via Distinct Mechanisms

Bryant-Li-Bhoj syndrome (BLBS) is caused by de novo mutations on histone H3.3 and is generally characterized by severe neurodevelopmental deficits. Oncogenic H3.3 amino acid substitutions were described over the past decade, but the molecular impact of BLBS mutations remained unstudied. The remarkable number and spread of the missense mutations led us to hypothesize that some converge on the same downstream effectors. We recently showed that H3.3G34R/V substitutions, seen in both cancer and BLBS, impair associations with the DNMT3A DNA methyltransferase. Our proteomic, enzymatic, and structural analyses now show that H3.3 BLBS mutations flanking glycine 34 have surprisingly stark effects on H3K36 methyltransferases, drastically altering H3K36 methyl states in cis and the binding of effector proteins with a PWWP domain, including DNMT3A/B. That confirms the existence of molecular commonalities amongst BLBS H3.3 point mutants while providing some of the first mechanistic insights into the syndrome.

molecular biology↗

bioRxiv2022

Antagonistic roles of canonical and alternative RPA in tandem CAG repeat diseases

Tandem CAG repeat expansion mutations cause >15 neurodegenerative diseases, where ongoing expansions in patients brains are thought to drive disease onset and progression. Repeat length mutations will involve single-stranded DNAs prone to form mutagenic DNA structures. However, the involvement of single-stranded DNA binding proteins (SSBs) in the prevention or formation of repeat instability is poorly understood. Here, we assessed the role of two SSBs, canonical RPA (RPA1-RPA2-RPA3) and the related Alternative-RPA (Alt-RPA, RPA1-RPA4-RPA3), where the primate-specific RPA4 replaces RPA2. RPA is essential for all forms of DNA metabolism, while Alt-RPA has undefined functions. RPA and Alt-RPA are upregulated 2- and 10-fold, respectively, in brains of Huntington disease (HD) and spinocerebellar ataxia type 1 (SCA1) patients. Correct repair of slipped-CAG DNA structures, intermediates of expansion mutations, is enhanced by RPA, but blocked by Alt-RPA. Slipped-DNAs are bound and melted more efficiently by RPA than by Alt-RPA. Removal of excess slipped-DNAs by FAN1 nuclease is enhanced by RPA, but blocked by Alt-RPA. Protein-protein interactomes (BioID) reveal unique and shared partners of RPA and Alt-RPA, including proteins involved in CAG instability and known modifiers of HD and SCA1 disease. RPA overexpression inhibits rampant CAG expansions in SCA1 mouse brains, coinciding with improved neuron morphology and rescued motor phenotypes. Thus, SSBs are involved in repeat length mutations, where Alt-RPA antagonistically blocks RPA from suppressing CAG expansions and hence pathogenesis. The processing of repeat length mutations is one example by which an Alt-RPA{leftrightarrow}RPA antagonistic interaction can affect outcomes, illuminating questions as to which of the many processes mediated by canonical RPA may also be modulated by Alt-RPA.

genetics↗