Biology subjects

Fulnecek, J.

Publications and source records attributed to Fulnecek, J..

4 recordsLinked to original sources

bioRxiv2026

Identification and characterization of a TRF2-like telomere-binding protein in Arabidopsis

Telomere protection and maintenance are mediated by proteins that bind telomeric DNA and recruit additional components of telomeric chromatin. While these factors are well characterized in yeast and mammals, their counterparts in plants remain poorly defined. Here, we used a proteomic approach in Arabidopsis thaliana to identify nuclear proteins that preferentially associate with telomeric DNA. We identified TRFL7, a previously uncharacterized member of the TRF-like (TRFL) protein family, as a prominent candidate. We show that TRFL7, together with its close homologues TRFL5 and TRFL11, associates with telomeric chromatin and forms distinct nuclear foci that preferentially localize near the nucleolus, resembling the nucleolus-associated telomere clustering characteristic of Arabidopsis. Genetic inactivation of TRFL7 in combination with either TRFL5 or TRFL11 results in telomere elongation, indicating a role for these proteins in telomere length homeostasis. Notably, TRFL7 contains an iDDR sequence motif that is also present in human TRF2, where it limits the activity of the Mre11-Rad50-Nbs1 complex. Together, our findings identify TRFL7 as a functional component of plant telomeric chromatin and suggest that it represents a plant orthologue of human TRF2.

molecular biology↗

bioRxiv2025

Post-transcriptional regulation of meiotic transcripts by the RNA binding protein CDM1 is associated with cytoplasmic condensate assemblies

The transition from diploid to haploid life phases requires extensive reprogramming of gene expression that drive meiotic cell division and the differentiation of haploid forms. A hallmark of meiosis is widespread post-transcriptional regulation, including delayed translation that ensures timely protein production at specific stages. Here, we identify a mechanism controlling the translation of meiotic transcripts in Arabidopsis pollen mother cells, mediated by CALLOSE DEFECTIVE MICROSPORES1 (CDM1). We show that CDM1 affects several meiotic processes, including chromosome pairing, condensation, and cytokinesis. CDM1 forms dynamic, meiosis specific cytoplasmic foci that associate with components of processing bodies and stress granules, giving rise to three-phase condensate assemblies. Biochemical and cellular analyses reveal that CDM1 is an RNA-binding protein with an intrinsic ability to form ribonucleoprotein condensates. Furthermore, we demonstrate that CDM1 binds mRNAs expressed in prophase I and represses their translation until later meiotic stages, coinciding with the disassembly of CDM1 condensates. These findings establish CDM1 as a key post-transcriptional regulator that fine-tunes the expression of meiotic genes to ensure proper progression of microsporogenesis.

plant biology↗

bioRxiv2023

SAP domain facilitates efficient loading of Ku onto DNA ends

Recognition and processing of DNA ends play a central role in maintaining genome integrity. The evolutionarily conserved DNA repair complex Ku serves as the primary sensor of free DNA ends in eukaryotic cells. Its rapid association with DNA ends is crucial for several cellular processes, including non-homologous end joining (NHEJ) DNA repair and telomere protection. In this study, we conducted a transient kinetic analysis to investigate the impact of the SAP domain on individual phases of the Ku-DNA interaction. Specifically, we examined the initial binding, the subsequent docking of Ku onto DNA, and the sliding of Ku along DNA. Our findings revealed that the C-terminal domain of Ku70, known as SAP ((SAF-A/B, Acinus and PIAS), facilitates the initial phases of Ku-DNA interaction, but does not affect the sliding process. This suggests that SAP may either establish the first interactions with DNA, or stabilize these initial interactions during loading. To assess the biological role of SAP, we generated Arabidopsis plants expressing Ku lacking the SAP domain ({Delta}SAP). Intriguingly, despite the decreased efficiency of the {Delta}SAP Ku complex in loading onto DNA, the mutant plants exhibited full proficiency in classical NHEJ and telomere maintenance. This indicates that the speed of Ku loading onto telomeres or DNA double-strand breaks (DSBs) is not the decisive factor in stabilizing these DNA structures.

molecular biology↗

bioRxiv2021

A CENH3 mutation promotes meiotic exit and restores fertility in SMG7-deficient Arabidopsis

Meiosis in angiosperm plants is followed by mitotic divisions to form multicellular haploid gametophytes. Termination of meiosis and transition to gametophytic development is, in Arabidopsis, governed by a dedicated mechanism that involves SMG7 and TDM1 proteins. Mutants carrying the smg7-6 allele are semi-fertile due to reduced pollen production. We found that instead of forming tetrads, smg7-6 pollen mother cells undergo multiple rounds of chromosome condensation and spindle assembly at the end of meiosis, resembling aberrant attempts to undergo additional meiotic divisions. A suppressor screen uncovered a mutation in centromeric histone H3 (CENH3) that increased fertility and promoted meiotic exit in smg7-6 plants. The mutation led to inefficient splicing of the CENH3 mRNA and a substantial decrease of CENH3, resulting in smaller centromeres. The reduced level of CENH3 delayed formation of the mitotic spindle but did not have an apparent effect on plant growth and development. We suggest that impaired spindle re-assembly at the end of meiosis limits aberrant divisions in smg7-6 plants and promotes formation of tetrads and viable pollen. Furthermore, the reduced level of CENH3 did not induce haploid plants in crosses with wild plants, indicating that differences in centromere size is not the key determinant of centromere-mediate genome elimination.

genetics↗